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2026-04-27net/sched: netem: check for negative latency and jitterStephen Hemminger1-0/+22
Reject requests with negative latency or jitter. A negative value added to current timestamp (u64) wraps to an enormous time_to_send, disabling dequeue. The original UAPI used u32 for these values; the conversion to 64-bit time values via TCA_NETEM_LATENCY64 and TCA_NETEM_JITTER64 allowed signed values to reach the kernel without validation. Jitter is already silently clamped by an abs() in netem_change(); that abs() can be removed in a follow-up once this rejection is in place. Fixes: 99803171ef04 ("netem: add uapi to express delay and jitter in nanoseconds") Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260418032027.900913-7-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-27net/sched: netem: fix slot delay calculation overflowStephen Hemminger1-3/+2
get_slot_next() computes a random delay between min_delay and max_delay using: get_random_u32() * (max_delay - min_delay) >> 32 This overflows signed 64-bit arithmetic when the delay range exceeds approximately 2.1 seconds (2^31 nanoseconds), producing a negative result that effectively disables slot-based pacing. This is a realistic configuration for WAN emulation (e.g., slot 1s 5s). Use mul_u64_u32_shr() which handles the widening multiply without overflow. Fixes: 0a9fe5c375b5 ("netem: slotting with non-uniform distribution") Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260418032027.900913-6-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-27net/sched: netem: validate slot configurationStephen Hemminger1-0/+29
Reject slot configurations that have no defensible meaning: - negative min_delay or max_delay - min_delay greater than max_delay - negative dist_delay or dist_jitter - negative max_packets or max_bytes Negative or out-of-order delays underflow in get_slot_next(), producing garbage intervals. Negative limits trip the per-slot accounting (packets_left/bytes_left <= 0) on the first packet of every slot, defeating the rate-limiting half of the slot feature. Note that dist_jitter has been silently coerced to its absolute value by get_slot() since the feature was introduced; rejecting negatives here converts that silent coercion into -EINVAL. The abs() can be removed in a follow-up. Fixes: 836af83b54e3 ("netem: support delivering packets in delayed time slots") Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260418032027.900913-5-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-27net/sched: netem: only reseed PRNG when seed is explicitly providedStephen Hemminger1-4/+6
netem_change() unconditionally reseeds the PRNG on every tc change command. If TCA_NETEM_PRNG_SEED is not specified, a new random seed is generated, destroying reproducibility for users who set a deterministic seed on a previous change. Move the initial random seed generation to netem_init() and only reseed in netem_change() when TCA_NETEM_PRNG_SEED is explicitly provided by the user. Fixes: 4072d97ddc44 ("netem: add prng attribute to netem_sched_data") Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260418032027.900913-4-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-27net/sched: netem: fix queue limit check to include reordered packetsStephen Hemminger1-1/+1
The queue limit check in netem_enqueue() uses q->t_len which only counts packets in the internal tfifo. Packets placed in sch->q by the reorder path (__qdisc_enqueue_head) are not counted, allowing the total queue occupancy to exceed sch->limit under reordering. Include sch->q.qlen in the limit check. Fixes: f8d4bc455047 ("net/sched: netem: account for backlog updates from child qdisc") Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260418032027.900913-3-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-27net/sched: netem: fix probability gaps in 4-state loss modelStephen Hemminger1-4/+4
The 4-state Markov chain in loss_4state() has gaps at the boundaries between transition probability ranges. The comparisons use: if (rnd < a4) else if (a4 < rnd && rnd < a1 + a4) When rnd equals a boundary value exactly, neither branch matches and no state transition occurs. The redundant lower-bound check (a4 < rnd) is already implied by being in the else branch. Remove the unnecessary lower-bound comparisons so the ranges are contiguous and every random value produces a transition, matching the GI (General and Intuitive) loss model specification. This bug goes back to original implementation of this model. Fixes: 661b79725fea ("netem: revised correlated loss generator") Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260418032027.900913-2-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-01net/sched: sch_netem: fix out-of-bounds access in packet corruptionYucheng Lu1-2/+3
In netem_enqueue(), the packet corruption logic uses get_random_u32_below(skb_headlen(skb)) to select an index for modifying skb->data. When an AF_PACKET TX_RING sends fully non-linear packets over an IPIP tunnel, skb_headlen(skb) evaluates to 0. Passing 0 to get_random_u32_below() takes the variable-ceil slow path which returns an unconstrained 32-bit random integer. Using this unconstrained value as an offset into skb->data results in an out-of-bounds memory access. Fix this by verifying skb_headlen(skb) is non-zero before attempting to corrupt the linear data area. Fully non-linear packets will silently bypass the corruption logic. Fixes: c865e5d99e25 ("[PKT_SCHED] netem: packet corruption option") Reported-by: Yifan Wu <yifanwucs@gmail.com> Reported-by: Juefei Pu <tomapufckgml@gmail.com> Signed-off-by: Yuan Tan <tanyuan98@outlook.com> Signed-off-by: Xin Liu <bird@lzu.edu.cn> Signed-off-by: Yuhang Zheng <z1652074432@gmail.com> Signed-off-by: Yucheng Lu <kanolyc@gmail.com> Reviewed-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://patch.msgid.link/45435c0935df877853a81e6d06205ac738ec65fa.1774941614.git.kanolyc@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-02-21Convert 'alloc_flex' family to use the new default GFP_KERNEL argumentLinus Torvalds1-1/+1
This is the exact same thing as the 'alloc_obj()' version, only much smaller because there are a lot fewer users of the *alloc_flex() interface. As with alloc_obj() version, this was done entirely with mindless brute force, using the same script, except using 'flex' in the pattern rather than 'objs*'. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2026-02-21treewide: Replace kmalloc with kmalloc_obj for non-scalar typesKees Cook1-1/+1
This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook <kees@kernel.org>
2025-11-25net_sched: use qdisc_skb_cb(skb)->pkt_segs in bstats_update()Eric Dumazet1-0/+1
Avoid up to two cache line misses in qdisc dequeue() to fetch skb_shinfo(skb)->gso_segs/gso_size while qdisc spinlock is held. This gives a 5 % improvement in a TX intensive workload. Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20251121083256.674562-6-edumazet@google.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-07-11net/sched: Restrict conditions for adding duplicating netems to qdisc treeWilliam Liu1-0/+40
netem_enqueue's duplication prevention logic breaks when a netem resides in a qdisc tree with other netems - this can lead to a soft lockup and OOM loop in netem_dequeue, as seen in [1]. Ensure that a duplicating netem cannot exist in a tree with other netems. Previous approaches suggested in discussions in chronological order: 1) Track duplication status or ttl in the sk_buff struct. Considered too specific a use case to extend such a struct, though this would be a resilient fix and address other previous and potential future DOS bugs like the one described in loopy fun [2]. 2) Restrict netem_enqueue recursion depth like in act_mirred with a per cpu variable. However, netem_dequeue can call enqueue on its child, and the depth restriction could be bypassed if the child is a netem. 3) Use the same approach as in 2, but add metadata in netem_skb_cb to handle the netem_dequeue case and track a packet's involvement in duplication. This is an overly complex approach, and Jamal notes that the skb cb can be overwritten to circumvent this safeguard. 4) Prevent the addition of a netem to a qdisc tree if its ancestral path contains a netem. However, filters and actions can cause a packet to change paths when re-enqueued to the root from netem duplication, leading us to the current solution: prevent a duplicating netem from inhabiting the same tree as other netems. [1] https://lore.kernel.org/netdev/8DuRWwfqjoRDLDmBMlIfbrsZg9Gx50DHJc1ilxsEBNe2D6NMoigR_eIRIG0LOjMc3r10nUUZtArXx4oZBIdUfZQrwjcQhdinnMis_0G7VEk=@willsroot.io/ [2] https://lwn.net/Articles/719297/ Fixes: 0afb51e72855 ("[PKT_SCHED]: netem: reinsert for duplication") Reported-by: William Liu <will@willsroot.io> Reported-by: Savino Dicanosa <savy@syst3mfailure.io> Signed-off-by: William Liu <will@willsroot.io> Signed-off-by: Savino Dicanosa <savy@syst3mfailure.io> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://patch.msgid.link/20250708164141.875402-1-will@willsroot.io Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-02-05netem: Update sch->q.qlen before qdisc_tree_reduce_backlog()Cong Wang1-1/+1
qdisc_tree_reduce_backlog() notifies parent qdisc only if child qdisc becomes empty, therefore we need to reduce the backlog of the child qdisc before calling it. Otherwise it would miss the opportunity to call cops->qlen_notify(), in the case of DRR, it resulted in UAF since DRR uses ->qlen_notify() to maintain its active list. Fixes: f8d4bc455047 ("net/sched: netem: account for backlog updates from child qdisc") Cc: Martin Ottens <martin.ottens@fau.de> Reported-by: Mingi Cho <mincho@theori.io> Signed-off-by: Cong Wang <cong.wang@bytedance.com> Link: https://patch.msgid.link/20250204005841.223511-4-xiyou.wangcong@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-12-11net/sched: netem: account for backlog updates from child qdiscMartin Ottens1-6/+16
In general, 'qlen' of any classful qdisc should keep track of the number of packets that the qdisc itself and all of its children holds. In case of netem, 'qlen' only accounts for the packets in its internal tfifo. When netem is used with a child qdisc, the child qdisc can use 'qdisc_tree_reduce_backlog' to inform its parent, netem, about created or dropped SKBs. This function updates 'qlen' and the backlog statistics of netem, but netem does not account for changes made by a child qdisc. 'qlen' then indicates the wrong number of packets in the tfifo. If a child qdisc creates new SKBs during enqueue and informs its parent about this, netem's 'qlen' value is increased. When netem dequeues the newly created SKBs from the child, the 'qlen' in netem is not updated. If 'qlen' reaches the configured sch->limit, the enqueue function stops working, even though the tfifo is not full. Reproduce the bug: Ensure that the sender machine has GSO enabled. Configure netem as root qdisc and tbf as its child on the outgoing interface of the machine as follows: $ tc qdisc add dev <oif> root handle 1: netem delay 100ms limit 100 $ tc qdisc add dev <oif> parent 1:0 tbf rate 50Mbit burst 1542 latency 50ms Send bulk TCP traffic out via this interface, e.g., by running an iPerf3 client on the machine. Check the qdisc statistics: $ tc -s qdisc show dev <oif> Statistics after 10s of iPerf3 TCP test before the fix (note that netem's backlog > limit, netem stopped accepting packets): qdisc netem 1: root refcnt 2 limit 1000 delay 100ms Sent 2767766 bytes 1848 pkt (dropped 652, overlimits 0 requeues 0) backlog 4294528236b 1155p requeues 0 qdisc tbf 10: parent 1:1 rate 50Mbit burst 1537b lat 50ms Sent 2767766 bytes 1848 pkt (dropped 327, overlimits 7601 requeues 0) backlog 0b 0p requeues 0 Statistics after the fix: qdisc netem 1: root refcnt 2 limit 1000 delay 100ms Sent 37766372 bytes 24974 pkt (dropped 9, overlimits 0 requeues 0) backlog 0b 0p requeues 0 qdisc tbf 10: parent 1:1 rate 50Mbit burst 1537b lat 50ms Sent 37766372 bytes 24974 pkt (dropped 327, overlimits 96017 requeues 0) backlog 0b 0p requeues 0 tbf segments the GSO SKBs (tbf_segment) and updates the netem's 'qlen'. The interface fully stops transferring packets and "locks". In this case, the child qdisc and tfifo are empty, but 'qlen' indicates the tfifo is at its limit and no more packets are accepted. This patch adds a counter for the entries in the tfifo. Netem's 'qlen' is only decreased when a packet is returned by its dequeue function, and not during enqueuing into the child qdisc. External updates to 'qlen' are thus accounted for and only the behavior of the backlog statistics changes. As in other qdiscs, 'qlen' then keeps track of how many packets are held in netem and all of its children. As before, sch->limit remains as the maximum number of packets in the tfifo. The same applies to netem's backlog statistics. Fixes: 50612537e9ab ("netem: fix classful handling") Signed-off-by: Martin Ottens <martin.ottens@fau.de> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://patch.msgid.link/20241210131412.1837202-1-martin.ottens@fau.de Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-10-03netem: Include <linux/prandom.h> in sch_netem.cUros Bizjak1-0/+1
Include <linux/prandom.h> header to allow the removal of legacy inclusion of <linux/prandom.h> from <linux/random.h>. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Cc: David S. Miller <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Acked-by: Stephen Hemminger <stephen@networkplumber.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2024-09-03sch/netem: fix use after free in netem_dequeueStephen Hemminger1-5/+4
If netem_dequeue() enqueues packet to inner qdisc and that qdisc returns __NET_XMIT_STOLEN. The packet is dropped but qdisc_tree_reduce_backlog() is not called to update the parent's q.qlen, leading to the similar use-after-free as Commit e04991a48dbaf382 ("netem: fix return value if duplicate enqueue fails") Commands to trigger KASAN UaF: ip link add type dummy ip link set lo up ip link set dummy0 up tc qdisc add dev lo parent root handle 1: drr tc filter add dev lo parent 1: basic classid 1:1 tc class add dev lo classid 1:1 drr tc qdisc add dev lo parent 1:1 handle 2: netem tc qdisc add dev lo parent 2: handle 3: drr tc filter add dev lo parent 3: basic classid 3:1 action mirred egress redirect dev dummy0 tc class add dev lo classid 3:1 drr ping -c1 -W0.01 localhost # Trigger bug tc class del dev lo classid 1:1 tc class add dev lo classid 1:1 drr ping -c1 -W0.01 localhost # UaF Fixes: 50612537e9ab ("netem: fix classful handling") Reported-by: Budimir Markovic <markovicbudimir@gmail.com> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://patch.msgid.link/20240901182438.4992-1-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-20netem: fix return value if duplicate enqueue failsStephen Hemminger1-18/+29
There is a bug in netem_enqueue() introduced by commit 5845f706388a ("net: netem: fix skb length BUG_ON in __skb_to_sgvec") that can lead to a use-after-free. This commit made netem_enqueue() always return NET_XMIT_SUCCESS when a packet is duplicated, which can cause the parent qdisc's q.qlen to be mistakenly incremented. When this happens qlen_notify() may be skipped on the parent during destruction, leaving a dangling pointer for some classful qdiscs like DRR. There are two ways for the bug happen: - If the duplicated packet is dropped by rootq->enqueue() and then the original packet is also dropped. - If rootq->enqueue() sends the duplicated packet to a different qdisc and the original packet is dropped. In both cases NET_XMIT_SUCCESS is returned even though no packets are enqueued at the netem qdisc. The fix is to defer the enqueue of the duplicate packet until after the original packet has been guaranteed to return NET_XMIT_SUCCESS. Fixes: 5845f706388a ("net: netem: fix skb length BUG_ON in __skb_to_sgvec") Reported-by: Budimir Markovic <markovicbudimir@gmail.com> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20240819175753.5151-1-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-02-02net/sched: Add module aliases for cls_,sch_,act_ modulesMichal Koutný1-0/+1
No functional change intended, aliases will be used in followup commits. Note for backporters: you may need to add aliases also for modules that are already removed in mainline kernel but still in your version. Patches were generated with the help of Coccinelle scripts like: cat >scripts/coccinelle/misc/tcf_alias.cocci <<EOD virtual patch virtual report @ haskernel @ @@ @ tcf_has_kind depends on report && haskernel @ identifier ops; constant K; @@ static struct tcf_proto_ops ops = { .kind = K, ... }; +char module_alias = K; EOD /usr/bin/spatch -D report --cocci-file scripts/coccinelle/misc/tcf_alias.cocci \ --dir . \ -I ./arch/x86/include -I ./arch/x86/include/generated -I ./include \ -I ./arch/x86/include/uapi -I ./arch/x86/include/generated/uapi \ -I ./include/uapi -I ./include/generated/uapi \ --include ./include/linux/compiler-version.h --include ./include/linux/kconfig.h \ --jobs 8 --chunksize 1 2>/dev/null | \ sed 's/char module_alias = "\([^"]*\)";/MODULE_ALIAS_NET_CLS("\1");/' And analogously for: static struct tc_action_ops ops = { .kind = K, static struct Qdisc_ops ops = { .id = K, (Someone familiar would be able to fit those into one .cocci file without sed post processing.) Signed-off-by: Michal Koutný <mkoutny@suse.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Reviewed-by: Jiri Pirko <jiri@nvidia.com> Link: https://lore.kernel.org/r/20240201130943.19536-3-mkoutny@suse.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-11-01net: sched: Fill in missing MODULE_DESCRIPTION for qdiscsVictor Nogueira1-0/+1
W=1 builds now warn if module is built without a MODULE_DESCRIPTION(). Fill in missing MODULE_DESCRIPTIONs for TC qdiscs. Signed-off-by: Victor Nogueira <victor@mojatatu.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com> Link: https://lore.kernel.org/r/20231027155045.46291-4-victor@mojatatu.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-10-05netem: Annotate struct disttable with __counted_byKees Cook1-1/+1
Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions). As found with Coccinelle[1], add __counted_by for struct disttable. Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1] Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Reviewed-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://lore.kernel.org/r/20231003231823.work.684-kees@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-08-17netem: use seeded PRNG for correlated loss eventsFrançois Michel1-10/+12
Use prandom_u32_state() instead of get_random_u32() to generate the correlated loss events of netem. Signed-off-by: François Michel <francois.michel@uclouvain.be> Reviewed-by: Simon Horman <horms@kernel.org> Acked-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://lore.kernel.org/r/20230815092348.1449179-4-francois.michel@uclouvain.be Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-08-17netem: use a seeded PRNG for generating random lossesFrançois Michel1-5/+6
Use prandom_u32_state() instead of get_random_u32() to generate the random loss events of netem. The state of the prng is part of the prng attribute of struct netem_sched_data. Signed-off-by: François Michel <francois.michel@uclouvain.be> Reviewed-by: Simon Horman <horms@kernel.org> Acked-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://lore.kernel.org/r/20230815092348.1449179-3-francois.michel@uclouvain.be Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-08-17netem: add prng attribute to netem_sched_dataFrançois Michel1-0/+16
Add prng attribute to struct netem_sched_data and allows setting the seed of the PRNG through netlink using the new TCA_NETEM_PRNG_SEED attribute. The PRNG attribute is not actually used yet. Signed-off-by: François Michel <francois.michel@uclouvain.be> Reviewed-by: Simon Horman <horms@kernel.org> Acked-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://lore.kernel.org/r/20230815092348.1449179-2-francois.michel@uclouvain.be Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-06-27Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski1-34/+25
Merge in late fixes to prepare for the 6.5 net-next PR. Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-06-24sch_netem: fix issues in netem_change() vs get_dist_table()Eric Dumazet1-34/+25
In blamed commit, I missed that get_dist_table() was allocating memory using GFP_KERNEL, and acquiring qdisc lock to perform the swap of newly allocated table with current one. In this patch, get_dist_table() is allocating memory and copy user data before we acquire the qdisc lock. Then we perform swap operations while being protected by the lock. Note that after this patch netem_change() no longer can do partial changes. If an error is returned, qdisc conf is left unchanged. Fixes: 2174a08db80d ("sch_netem: acquire qdisc lock in netem_change()") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Link: https://lore.kernel.org/r/20230622181503.2327695-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-06-22Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski1-2/+6
Cross-merge networking fixes after downstream PR. Conflicts: tools/testing/selftests/net/fcnal-test.sh d7a2fc1437f7 ("selftests: net: fcnal-test: check if FIPS mode is enabled") dd017c72dde6 ("selftests: fcnal: Test SO_DONTROUTE on TCP sockets.") https://lore.kernel.org/all/5007b52c-dd16-dbf6-8d64-b9701bfa498b@tessares.net/ https://lore.kernel.org/all/20230619105427.4a0df9b3@canb.auug.org.au/ No adjacent changes. Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-06-22sch_netem: acquire qdisc lock in netem_change()Eric Dumazet1-2/+6
syzbot managed to trigger a divide error [1] in netem. It could happen if q->rate changes while netem_enqueue() is running, since q->rate is read twice. It turns out netem_change() always lacked proper synchronization. [1] divide error: 0000 [#1] SMP KASAN CPU: 1 PID: 7867 Comm: syz-executor.1 Not tainted 6.1.30-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023 RIP: 0010:div64_u64 include/linux/math64.h:69 [inline] RIP: 0010:packet_time_ns net/sched/sch_netem.c:357 [inline] RIP: 0010:netem_enqueue+0x2067/0x36d0 net/sched/sch_netem.c:576 Code: 89 e2 48 69 da 00 ca 9a 3b 42 80 3c 28 00 4c 8b a4 24 88 00 00 00 74 0d 4c 89 e7 e8 c3 4f 3b fd 48 8b 4c 24 18 48 89 d8 31 d2 <49> f7 34 24 49 01 c7 4c 8b 64 24 48 4d 01 f7 4c 89 e3 48 c1 eb 03 RSP: 0018:ffffc9000dccea60 EFLAGS: 00010246 RAX: 000001a442624200 RBX: 000001a442624200 RCX: ffff888108a4f000 RDX: 0000000000000000 RSI: 000000000000070d RDI: 000000000000070d RBP: ffffc9000dcceb90 R08: ffffffff849c5e26 R09: fffffbfff10e1297 R10: 0000000000000000 R11: dffffc0000000001 R12: ffff888108a4f358 R13: dffffc0000000000 R14: 0000001a8cd9a7ec R15: 0000000000000000 FS: 00007fa73fe18700(0000) GS:ffff8881f6b00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa73fdf7718 CR3: 000000011d36e000 CR4: 0000000000350ee0 Call Trace: <TASK> [<ffffffff84714385>] __dev_xmit_skb net/core/dev.c:3931 [inline] [<ffffffff84714385>] __dev_queue_xmit+0xcf5/0x3370 net/core/dev.c:4290 [<ffffffff84d22df2>] dev_queue_xmit include/linux/netdevice.h:3030 [inline] [<ffffffff84d22df2>] neigh_hh_output include/net/neighbour.h:531 [inline] [<ffffffff84d22df2>] neigh_output include/net/neighbour.h:545 [inline] [<ffffffff84d22df2>] ip_finish_output2+0xb92/0x10d0 net/ipv4/ip_output.c:235 [<ffffffff84d21e63>] __ip_finish_output+0xc3/0x2b0 [<ffffffff84d10a81>] ip_finish_output+0x31/0x2a0 net/ipv4/ip_output.c:323 [<ffffffff84d10f14>] NF_HOOK_COND include/linux/netfilter.h:298 [inline] [<ffffffff84d10f14>] ip_output+0x224/0x2a0 net/ipv4/ip_output.c:437 [<ffffffff84d123b5>] dst_output include/net/dst.h:444 [inline] [<ffffffff84d123b5>] ip_local_out net/ipv4/ip_output.c:127 [inline] [<ffffffff84d123b5>] __ip_queue_xmit+0x1425/0x2000 net/ipv4/ip_output.c:542 [<ffffffff84d12fdc>] ip_queue_xmit+0x4c/0x70 net/ipv4/ip_output.c:556 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Link: https://lore.kernel.org/r/20230620184425.1179809-1-edumazet@google.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2023-06-10net: move gso declarations and functions to their own filesEric Dumazet1-0/+1
Move declarations into include/net/gso.h and code into net/core/gso.c Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Stanislav Fomichev <sdf@google.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Reviewed-by: David Ahern <dsahern@kernel.org> Link: https://lore.kernel.org/r/20230608191738.3947077-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-11-18treewide: use get_random_u32_below() instead of deprecated functionJason A. Donenfeld1-2/+2
This is a simple mechanical transformation done by: @@ expression E; @@ - prandom_u32_max + get_random_u32_below (E) Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs Reviewed-by: SeongJae Park <sj@kernel.org> # for damon Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> # for infiniband Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> # for arm Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-10-11treewide: use get_random_u32() when possibleJason A. Donenfeld1-9/+9
The prandom_u32() function has been a deprecated inline wrapper around get_random_u32() for several releases now, and compiles down to the exact same code. Replace the deprecated wrapper with a direct call to the real function. The same also applies to get_random_int(), which is just a wrapper around get_random_u32(). This was done as a basic find and replace. Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Yury Norov <yury.norov@gmail.com> Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 Acked-by: Toke Høiland-Jørgensen <toke@toke.dk> # for sch_cake Acked-by: Chuck Lever <chuck.lever@oracle.com> # for nfsd Acked-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> # for thunderbolt Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs Acked-by: Helge Deller <deller@gmx.de> # for parisc Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-10-11treewide: use prandom_u32_max() when possible, part 1Jason A. Donenfeld1-2/+2
Rather than incurring a division or requesting too many random bytes for the given range, use the prandom_u32_max() function, which only takes the minimum required bytes from the RNG and avoids divisions. This was done mechanically with this coccinelle script: @basic@ expression E; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; typedef u64; @@ ( - ((T)get_random_u32() % (E)) + prandom_u32_max(E) | - ((T)get_random_u32() & ((E) - 1)) + prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2) | - ((u64)(E) * get_random_u32() >> 32) + prandom_u32_max(E) | - ((T)get_random_u32() & ~PAGE_MASK) + prandom_u32_max(PAGE_SIZE) ) @multi_line@ identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; identifier RAND; expression E; @@ - RAND = get_random_u32(); ... when != RAND - RAND %= (E); + RAND = prandom_u32_max(E); // Find a potential literal @literal_mask@ expression LITERAL; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; position p; @@ ((T)get_random_u32()@p & (LITERAL)) // Add one to the literal. @script:python add_one@ literal << literal_mask.LITERAL; RESULT; @@ value = None if literal.startswith('0x'): value = int(literal, 16) elif literal[0] in '123456789': value = int(literal, 10) if value is None: print("I don't know how to handle %s" % (literal)) cocci.include_match(False) elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1: print("Skipping 0x%x for cleanup elsewhere" % (value)) cocci.include_match(False) elif value & (value + 1) != 0: print("Skipping 0x%x because it's not a power of two minus one" % (value)) cocci.include_match(False) elif literal.startswith('0x'): coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1)) else: coccinelle.RESULT = cocci.make_expr("%d" % (value + 1)) // Replace the literal mask with the calculated result. @plus_one@ expression literal_mask.LITERAL; position literal_mask.p; expression add_one.RESULT; identifier FUNC; @@ - (FUNC()@p & (LITERAL)) + prandom_u32_max(RESULT) @collapse_ret@ type T; identifier VAR; expression E; @@ { - T VAR; - VAR = (E); - return VAR; + return E; } @drop_var@ type T; identifier VAR; @@ { - T VAR; ... when != VAR } Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Yury Norov <yury.norov@gmail.com> Reviewed-by: KP Singh <kpsingh@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd Acked-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390 Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-09-22net/sched: use tc_qdisc_stats_dump() in qdiscZhengchao Shao1-6/+2
use tc_qdisc_stats_dump() in qdisc. Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com> Reviewed-by: Victor Nogueira <victor@mojatatu.com> Tested-by: Victor Nogueira <victor@mojatatu.com> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-09-01net: sched: remove redundant NULL check in change hook functionZhengchao Shao1-3/+0
Currently, the change function can be called by two ways. The one way is that qdisc_change() will call it. Before calling change function, qdisc_change() ensures tca[TCA_OPTIONS] is not empty. The other way is that .init() will call it. The opt parameter is also checked before calling change function in .init(). Therefore, it's no need to check the input parameter opt in change function. Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com> Acked-by: Toke Høiland-Jørgensen <toke@toke.dk> Link: https://lore.kernel.org/r/20220829071219.208646-1-shaozhengchao@huawei.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2022-06-17net/sched: sch_netem: Fix arithmetic in netem_dump() for 32-bit platformsPeilin Ye1-2/+2
As reported by Yuming, currently tc always show a latency of UINT_MAX for netem Qdisc's on 32-bit platforms: $ tc qdisc add dev dummy0 root netem latency 100ms $ tc qdisc show dev dummy0 qdisc netem 8001: root refcnt 2 limit 1000 delay 275s 275s ^^^^^^^^^^^^^^^^ Let us take a closer look at netem_dump(): qopt.latency = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->latency, UINT_MAX); qopt.latency is __u32, psched_tdiff_t is signed long, (psched_tdiff_t)(UINT_MAX) is negative for 32-bit platforms, so qopt.latency is always UINT_MAX. Fix it by using psched_time_t (u64) instead. Note: confusingly, users have two ways to specify 'latency': 1. normally, via '__u32 latency' in struct tc_netem_qopt; 2. via the TCA_NETEM_LATENCY64 attribute, which is s64. For the second case, theoretically 'latency' could be negative. This patch ignores that corner case, since it is broken (i.e. assigning a negative s64 to __u32) anyways, and should be handled separately. Thanks Ted Lin for the analysis [1] . [1] https://github.com/raspberrypi/linux/issues/3512 Reported-by: Yuming Chen <chenyuming.junnan@bytedance.com> Fixes: 112f9cb65643 ("netem: convert to qdisc_watchdog_schedule_ns") Reviewed-by: Cong Wang <cong.wang@bytedance.com> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com> Acked-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://lore.kernel.org/r/20220616234336.2443-1-yepeilin.cs@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-11-15net: sched: sch_netem: Refactor code in 4-state loss generatorHarshit Mogalapalli1-9/+9
Fixed comments to match description with variable names and refactored code to match the convention as per [1]. To match the convention mapping is done as follows: State 3 - LOST_IN_BURST_PERIOD State 4 - LOST_IN_GAP_PERIOD [1] S. Salsano, F. Ludovici, A. Ordine, "Definition of a general and intuitive loss model for packet networks and its implementation in the Netem module in the Linux kernel" Fixes: a6e2fe17eba4 ("sch_netem: replace magic numbers with enumerate") Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com> Acked-by: Stephen Hemminger <stephen@networkplumber.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2021-09-30net: sched: Use struct_size() helper in kvmalloc()Gustavo A. R. Silva1-1/+1
Make use of the struct_size() helper instead of an open-coded version, in order to avoid any potential type mistakes or integer overflows that, in the worst scenario, could lead to heap overflows. Link: https://github.com/KSPP/linux/issues/160 Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Link: https://lore.kernel.org/r/20210929201718.GA342296@embeddedor Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-10-29netem: fix zero division in tabledistAleksandr Nogikh1-1/+8
Currently it is possible to craft a special netlink RTM_NEWQDISC command that can result in jitter being equal to 0x80000000. It is enough to set the 32 bit jitter to 0x02000000 (it will later be multiplied by 2^6) or just set the 64 bit jitter via TCA_NETEM_JITTER64. This causes an overflow during the generation of uniformly distributed numbers in tabledist(), which in turn leads to division by zero (sigma != 0, but sigma * 2 is 0). The related fragment of code needs 32-bit division - see commit 9b0ed89 ("netem: remove unnecessary 64 bit modulus"), so switching to 64 bit is not an option. Fix the issue by keeping the value of jitter within the range that can be adequately handled by tabledist() - [0;INT_MAX]. As negative std deviation makes no sense, take the absolute value of the passed value and cap it at INT_MAX. Inside tabledist(), switch to unsigned 32 bit arithmetic in order to prevent overflows. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Aleksandr Nogikh <nogikh@google.com> Reported-by: syzbot+ec762a6342ad0d3c0d8f@syzkaller.appspotmail.com Acked-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://lore.kernel.org/r/20201028170731.1383332-1-aleksandrnogikh@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-02-29net: sched: Replace zero-length array with flexible-array memberGustavo A. R. Silva1-1/+1
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2019-10-19net: netem: correct the parent's backlog when corrupted packet was droppedJakub Kicinski1-0/+2
If packet corruption failed we jump to finish_segs and return NET_XMIT_SUCCESS. Seeing success will make the parent qdisc increment its backlog, that's incorrect - we need to return NET_XMIT_DROP. Fixes: 6071bd1aa13e ("netem: Segment GSO packets on enqueue") Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Simon Horman <simon.horman@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2019-10-19net: netem: fix error path for corrupted GSO framesJakub Kicinski1-3/+6
To corrupt a GSO frame we first perform segmentation. We then proceed using the first segment instead of the full GSO skb and requeue the rest of the segments as separate packets. If there are any issues with processing the first segment we still want to process the rest, therefore we jump to the finish_segs label. Commit 177b8007463c ("net: netem: fix backlog accounting for corrupted GSO frames") started using the pointer to the first segment in the "rest of segments processing", but as mentioned above the first segment may had already been freed at this point. Backlog corrections for parent qdiscs have to be adjusted. Fixes: 177b8007463c ("net: netem: fix backlog accounting for corrupted GSO frames") Reported-by: kbuild test robot <lkp@intel.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Reported-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Simon Horman <simon.horman@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2019-09-27sch_netem: fix rcu splat in netem_enqueue()Eric Dumazet1-1/+1
qdisc_root() use from netem_enqueue() triggers a lockdep warning. __dev_queue_xmit() uses rcu_read_lock_bh() which is not equivalent to rcu_read_lock() + local_bh_disable_bh as far as lockdep is concerned. WARNING: suspicious RCU usage 5.3.0-rc7+ #0 Not tainted ----------------------------- include/net/sch_generic.h:492 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by syz-executor427/8855: #0: 00000000b5525c01 (rcu_read_lock_bh){....}, at: lwtunnel_xmit_redirect include/net/lwtunnel.h:92 [inline] #0: 00000000b5525c01 (rcu_read_lock_bh){....}, at: ip_finish_output2+0x2dc/0x2570 net/ipv4/ip_output.c:214 #1: 00000000b5525c01 (rcu_read_lock_bh){....}, at: __dev_queue_xmit+0x20a/0x3650 net/core/dev.c:3804 #2: 00000000364bae92 (&(&sch->q.lock)->rlock){+.-.}, at: spin_lock include/linux/spinlock.h:338 [inline] #2: 00000000364bae92 (&(&sch->q.lock)->rlock){+.-.}, at: __dev_xmit_skb net/core/dev.c:3502 [inline] #2: 00000000364bae92 (&(&sch->q.lock)->rlock){+.-.}, at: __dev_queue_xmit+0x14b8/0x3650 net/core/dev.c:3838 stack backtrace: CPU: 0 PID: 8855 Comm: syz-executor427 Not tainted 5.3.0-rc7+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 lockdep_rcu_suspicious+0x153/0x15d kernel/locking/lockdep.c:5357 qdisc_root include/net/sch_generic.h:492 [inline] netem_enqueue+0x1cfb/0x2d80 net/sched/sch_netem.c:479 __dev_xmit_skb net/core/dev.c:3527 [inline] __dev_queue_xmit+0x15d2/0x3650 net/core/dev.c:3838 dev_queue_xmit+0x18/0x20 net/core/dev.c:3902 neigh_hh_output include/net/neighbour.h:500 [inline] neigh_output include/net/neighbour.h:509 [inline] ip_finish_output2+0x1726/0x2570 net/ipv4/ip_output.c:228 __ip_finish_output net/ipv4/ip_output.c:308 [inline] __ip_finish_output+0x5fc/0xb90 net/ipv4/ip_output.c:290 ip_finish_output+0x38/0x1f0 net/ipv4/ip_output.c:318 NF_HOOK_COND include/linux/netfilter.h:294 [inline] ip_mc_output+0x292/0xf40 net/ipv4/ip_output.c:417 dst_output include/net/dst.h:436 [inline] ip_local_out+0xbb/0x190 net/ipv4/ip_output.c:125 ip_send_skb+0x42/0xf0 net/ipv4/ip_output.c:1555 udp_send_skb.isra.0+0x6b2/0x1160 net/ipv4/udp.c:887 udp_sendmsg+0x1e96/0x2820 net/ipv4/udp.c:1174 inet_sendmsg+0x9e/0xe0 net/ipv4/af_inet.c:807 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0xd7/0x130 net/socket.c:657 ___sys_sendmsg+0x3e2/0x920 net/socket.c:2311 __sys_sendmmsg+0x1bf/0x4d0 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2439 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2019-09-20sch_netem: fix a divide by zero in tabledist()Eric Dumazet1-1/+1
syzbot managed to crash the kernel in tabledist() loading an empty distribution table. t = dist->table[rnd % dist->size]; Simply return an