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bpf: Fix updating attached freplace prog in prog_array map

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The commit f7866c3587 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT")
fixed a NULL pointer dereference panic, but didn't fix the issue that
fails to update attached freplace prog to prog_array map.

Since commit 1c123c567f ("bpf: Resolve fext program type when checking map compatibility"),
freplace prog and its target prog are able to tail call each other.

And the commit 3aac1ead5e ("bpf: Move prog->aux->linked_prog and trampoline into bpf_link on attach")
sets prog->aux->dst_prog as NULL after attaching freplace prog to its
target prog.

After loading freplace the prog_array's owner type is BPF_PROG_TYPE_SCHED_CLS.
Then, after attaching freplace its prog->aux->dst_prog is NULL.
Then, while updating freplace in prog_array the bpf_prog_map_compatible()
incorrectly returns false because resolve_prog_type() returns
BPF_PROG_TYPE_EXT instead of BPF_PROG_TYPE_SCHED_CLS.
After this patch the resolve_prog_type() returns BPF_PROG_TYPE_SCHED_CLS
and update to prog_array can succeed.

Fixes: f7866c3587 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT")
Cc: Toke Høiland-Jørgensen <toke@redhat.com>
Cc: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20240728114612.48486-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Leon Hwang 2024-07-28 19:46:11 +08:00 committed by Alexei Starovoitov
parent d74da84604
commit fdad456cbc
1 changed files with 2 additions and 2 deletions
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4
include/linux/bpf_verifier.h
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@ -856,8 +856,8 @@ static inline u32 type_flag(u32 type)
/* only use after check_attach_btf_id() */
static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)
{
return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->dst_prog) ?
prog->aux->dst_prog->type : prog->type;
return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->saved_dst_prog_type) ?
prog->aux->saved_dst_prog_type : prog->type;
}
static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)