6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Leon Hwang <leon.hwang@xxxxxxxxx>
[ 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@xxxxxxxxxx>
Cc: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240728114612.48486-2-leon.hwang@xxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 b62535fd8de5f..92919d52f7e1b 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -760,8 +760,8 @@ 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)
--
2.43.0
