6.1-stable review patch. If anyone has any objections, please let me know.
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From: Leon Hwang leon.hwang@linux.dev
[ Upstream commit fdad456cbcca739bae1849549c7a999857c56f88 ]
The commit f7866c358733 ("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 1c123c567fb1 ("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 3aac1ead5eb6 ("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: f7866c358733 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/bpf_verifier.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 6a524c5462a6f..131adc98080b8 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -645,8 +645,8 @@ 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)