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libbpf: Fix null-pointer dereference in find_prog_by_sec_insn() 

When there are no program sections, obj->programs is left unallocated,
and find_prog_by_sec_insn()'s search lands on &obj->programs[0] == NULL,
and will cause null-pointer dereference in the following access to
prog->sec_idx.

Guard the search with obj->nr_programs similar to what's being done in
__bpf_program__iter() to prevent null-pointer access from happening.

Fixes: db2b8b0642 ("libbpf: Support CO-RE relocations for multi-prog sections")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221012022353.7350-4-shung-hsi.yu@suse.com
This commit is contained in:
Shung-Hsi Yu 2022-10-12 10:23:53 +08:00 committed by Andrii Nakryiko
parent 35a855509e
commit d0d382f95a
1 changed files with 3 additions and 0 deletions
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3
tools/lib/bpf/libbpf.c
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@ -4115,6 +4115,9 @@ static struct bpf_program *find_prog_by_sec_insn(const struct bpf_object *obj,
int l = 0, r = obj->nr_programs - 1, m; int l = 0, r = obj->nr_programs - 1, m;
struct bpf_program *prog; struct bpf_program *prog;
if (!obj->nr_programs)
return NULL;
while (l < r) { while (l < r) {
m = l + (r - l + 1) / 2; m = l + (r - l + 1) / 2;
prog = &obj->programs[m]; prog = &obj->programs[m];