diff options
| author | Weiming Shi <bestswngs@gmail.com> | 2026-09-15 01:02:07 +0800 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2026-09-17 15:00:17 -0700 |
| commit | 50e80e2bb5e2be8515205b9c496b9640ddefa434 (patch) | |
| tree | 64e3464f7df0f2dfe541d80a9a812c7e81e3541e /kernel | |
| parent | 70504de0bb627848667207bec7ccfd647deb8814 (diff) | |
bpf: Skip unsettled links in link iterator
bpf_link_prime() inserts a link into link_idr before anon_inode_getfile()
succeeds and before bpf_link_settle() publishes the ID in link->id.
bpf_link_by_id() treats such an ID-zero link as unsettled, but the link
iterator takes a reference without this check.
If anon_inode_getfile() then fails, the creator removes the ID and frees
its still-private link directly. The iterator is left with a dangling
reference and its next bpf_link_put() accesses freed memory.
Treat ID-zero entries as transient in bpf_link_get_curr_or_next(), just as
bpf_link_by_id() does.
BUG: KASAN: slab-use-after-free in bpf_link_put
Write of size 8 by task exp/384
Call Trace:
bpf_link_put kernel/bpf/syscall.c:3372
bpf_link_seq_next kernel/bpf/link_iter.c:33
bpf_seq_read kernel/bpf/bpf_iter.c:158
vfs_read fs/read_write.c:572
ksys_read fs/read_write.c:716
do_syscall_64 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe arch/x86/entry/entry_64.S:121
Kernel panic - not syncing: KASAN: panic_on_warn set ...
Fixes: 9f8836127308 ("bpf: Add bpf_link iterator")
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260914170206.170723-2-bestswngs@gmail.com
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/syscall.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 853b47f81384..244a939b9d2d 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -6042,7 +6042,10 @@ struct bpf_link *bpf_link_get_curr_or_next(u32 *id) again: link = idr_get_next(&link_idr, id); if (link) { - link = bpf_link_inc_not_zero(link); + if (link->id) + link = bpf_link_inc_not_zero(link); + else + link = ERR_PTR(-EAGAIN); if (IS_ERR(link)) { (*id)++; goto again; |