From 14a324f6a67ef6a53e04362a70160a47eb8afffa Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Mon, 25 Apr 2022 03:18:55 +0530 Subject: bpf: Wire up freeing of referenced kptr A destructor kfunc can be defined as void func(type *), where type may be void or any other pointer type as per convenience. In this patch, we ensure that the type is sane and capture the function pointer into off_desc of ptr_off_tab for the specific pointer offset, with the invariant that the dtor pointer is always set when 'kptr_ref' tag is applied to the pointer's pointee type, which is indicated by the flag BPF_MAP_VALUE_OFF_F_REF. Note that only BTF IDs whose destructor kfunc is registered, thus become the allowed BTF IDs for embedding as referenced kptr. Hence it serves the purpose of finding dtor kfunc BTF ID, as well acting as a check against the whitelist of allowed BTF IDs for this purpose. Finally, wire up the actual freeing of the referenced pointer if any at all available offsets, so that no references are leaked after the BPF map goes away and the BPF program previously moved the ownership a referenced pointer into it. The behavior is similar to BPF timers, where bpf_map_{update,delete}_elem will free any existing referenced kptr. The same case is with LRU map's bpf_lru_push_free/htab_lru_push_free functions, which are extended to reset unreferenced and free referenced kptr. Note that unlike BPF timers, kptr is not reset or freed when map uref drops to zero. Signed-off-by: Kumar Kartikeya Dwivedi Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20220424214901.2743946-8-memxor@gmail.com --- kernel/bpf/arraymap.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'kernel/bpf/arraymap.c') diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 7f145aefbff8..c3de63ce574e 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -287,10 +287,12 @@ static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key return 0; } -static void check_and_free_timer_in_array(struct bpf_array *arr, void *val) +static void check_and_free_fields(struct bpf_array *arr, void *val) { - if (unlikely(map_value_has_timer(&arr->map))) + if (map_value_has_timer(&arr->map)) bpf_timer_cancel_and_free(val + arr->map.timer_off); + if (map_value_has_kptrs(&arr->map)) + bpf_map_free_kptrs(&arr->map, val); } /* Called from syscall or from eBPF program */ @@ -327,7 +329,7 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value, copy_map_value_locked(map, val, value, false); else copy_map_value(map, val, value); - check_and_free_timer_in_array(array, val); + check_and_free_fields(array, val); } return 0; } @@ -386,7 +388,8 @@ static void array_map_free_timers(struct bpf_map *map) struct bpf_array *array = container_of(map, struct bpf_array, map); int i; - if (likely(!map_value_has_timer(map))) + /* We don't reset or free kptr on uref dropping to zero. */ + if (!map_value_has_timer(map)) return; for (i = 0; i < array->map.max_entries; i++) @@ -398,6 +401,13 @@ static void array_map_free_timers(struct bpf_map *map) static void array_map_free(struct bpf_map *map) { struct bpf_array *array = container_of(map, struct bpf_array, map); + int i; + + if (map_value_has_kptrs(map)) { + for (i = 0; i < array->map.max_entries; i++) + bpf_map_free_kptrs(map, array->value + array->elem_size * i); + bpf_map_free_kptr_off_tab(map); + } if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY) bpf_array_free_percpu(array); -- cgit v1.2.3 From c317ab71facc2cd0a94145973318a4c914e11acc Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Mon, 25 Apr 2022 21:32:47 +0800 Subject: bpf: Compute map_btf_id during build time For now, the field 'map_btf_id' in 'struct bpf_map_ops' for all map types are computed during vmlinux-btf init: btf_parse_vmlinux() -> btf_vmlinux_map_ids_init() It will lookup the btf_type according to the 'map_btf_name' field in 'struct bpf_map_ops'. This process can be done during build time, thanks to Jiri's resolve_btfids. selftest of map_ptr has passed: $96 map_ptr:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Reported-by: kernel test robot Signed-off-by: Menglong Dong Signed-off-by: Alexei Starovoitov --- kernel/bpf/arraymap.c | 26 ++++++++------------------ 1 file changed, 8 insertions(+), 18 deletions(-) (limited to 'kernel/bpf/arraymap.c') diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index c3de63ce574e..b3bf31fd9458 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -11,6 +11,7 @@ #include #include #include +#include #include "map_in_map.h" @@ -690,7 +691,7 @@ static int bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_ return num_elems; } -static int array_map_btf_id; +BTF_ID_LIST_SINGLE(array_map_btf_ids, struct, bpf_array) const struct bpf_map_ops array_map_ops = { .map_meta_equal = array_map_meta_equal, .map_alloc_check = array_map_alloc_check, @@ -711,12 +712,10 @@ const struct bpf_map_ops array_map_ops = { .map_update_batch = generic_map_update_batch, .map_set_for_each_callback_args = map_set_for_each_callback_args, .map_for_each_callback = bpf_for_each_array_elem, - .map_btf_name = "bpf_array", - .map_btf_id = &array_map_btf_id, + .map_btf_id = &array_map_btf_ids[0], .iter_seq_info = &iter_seq_info, }; -static int percpu_array_map_btf_id; const struct bpf_map_ops percpu_array_map_ops = { .map_meta_equal = bpf_map_meta_equal, .map_alloc_check = array_map_alloc_check, @@ -732,8 +731,7 @@ const struct bpf_map_ops percpu_array_map_ops = { .map_update_batch = generic_map_update_batch, .map_set_for_each_callback_args = map_set_for_each_callback_args, .map_for_each_callback = bpf_for_each_array_elem, - .map_btf_name = "bpf_array", - .map_btf_id = &percpu_array_map_btf_id, + .map_btf_id = &array_map_btf_ids[0], .iter_seq_info = &iter_seq_info, }; @@ -1112,7 +1110,6 @@ static void prog_array_map_free(struct bpf_map *map) * Thus, prog_array_map cannot be used as an inner_map * and map_meta_equal is not implemented. */ -static int prog_array_map_btf_id; const struct bpf_map_ops prog_array_map_ops = { .map_alloc_check = fd_array_map_alloc_check, .map_alloc = prog_array_map_alloc, @@ -1128,8 +1125,7 @@ const struct bpf_map_ops prog_array_map_ops = { .map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem, .map_release_uref = prog_array_map_clear, .map_seq_show_elem = prog_array_map_seq_show_elem, - .map_btf_name = "bpf_array", - .map_btf_id = &prog_array_map_btf_id, + .map_btf_id = &array_map_btf_ids[0], }; static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file, @@ -1218,7 +1214,6 @@ static void perf_event_fd_array_map_free(struct bpf_map *map) fd_array_map_free(map); } -static int perf_event_array_map_btf_id; const struct bpf_map_ops perf_event_array_map_ops = { .map_meta_equal = bpf_map_meta_equal, .map_alloc_check = fd_array_map_alloc_check, @@ -1231,8 +1226,7 @@ const struct bpf_map_ops perf_event_array_map_ops = { .map_fd_put_ptr = perf_event_fd_array_put_ptr, .map_release = perf_event_fd_array_release, .map_check_btf = map_check_no_btf, - .map_btf_name = "bpf_array", - .map_btf_id = &perf_event_array_map_btf_id, + .map_btf_id = &array_map_btf_ids[0], }; #ifdef CONFIG_CGROUPS @@ -1255,7 +1249,6 @@ static void cgroup_fd_array_free(struct bpf_map *map) fd_array_map_free(map); } -static int cgroup_array_map_btf_id; const struct bpf_map_ops cgroup_array_map_ops = { .map_meta_equal = bpf_map_meta_equal, .map_alloc_check = fd_array_map_alloc_check, @@ -1267,8 +1260,7 @@ const struct bpf_map_ops cgroup_array_map_ops = { .map_fd_get_ptr = cgroup_fd_array_get_ptr, .map_fd_put_ptr = cgroup_fd_array_put_ptr, .map_check_btf = map_check_no_btf, - .map_btf_name = "bpf_array", - .map_btf_id = &cgroup_array_map_btf_id, + .map_btf_id = &array_map_btf_ids[0], }; #endif @@ -1342,7 +1334,6 @@ static int array_of_map_gen_lookup(struct bpf_map *map, return insn - insn_buf; } -static int array_of_maps_map_btf_id; const struct bpf_map_ops array_of_maps_map_ops = { .map_alloc_check = fd_array_map_alloc_check, .map_alloc = array_of_map_alloc, @@ -1355,6 +1346,5 @@ const struct bpf_map_ops array_of_maps_map_ops = { .map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem, .map_gen_lookup = array_of_map_gen_lookup, .map_check_btf = map_check_no_btf, - .map_btf_name = "bpf_array", - .map_btf_id = &array_of_maps_map_btf_id, + .map_btf_id = &array_map_btf_ids[0], }; -- cgit v1.2.3