This is a note to let you know that I've just added the patch titled
bpf: disallow attaching modify_return tracing functions to other BPF programs
to the 5.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-disallow-attaching-modify_return-tracing-functio.patch
and it can be found in the queue-5.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit c1fe1cb5873ca1c260cccb05be97014a3bb35352
Author: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Date: Fri Sep 25 23:25:00 2020 +0200
bpf: disallow attaching modify_return tracing functions to other BPF programs
[ Upstream commit 1af9270e908cd50a4f5d815c9b6f794c7d57ed07 ]
From the checks and commit messages for modify_return, it seems it was
never the intention that it should be possible to attach a tracing program
with expected_attach_type == BPF_MODIFY_RETURN to another BPF program.
However, check_attach_modify_return() will only look at the function name,
so if the target function starts with "security_", the attach will be
allowed even for bpf2bpf attachment.
Fix this oversight by also blocking the modification if a target program is
supplied.
Fixes: 18644cec714a ("bpf: Fix use-after-free in fmod_ret check")
Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 89b07db146763..c953dfbbaa6a9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10862,6 +10862,11 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
}
if (prog->expected_attach_type == BPF_MODIFY_RETURN) {
+ if (tgt_prog) {
+ verbose(env, "can't modify return codes of BPF programs\n");
+ ret = -EINVAL;
+ goto out;
+ }
ret = check_attach_modify_return(prog, addr);
if (ret)
verbose(env, "%s() is not modifiable\n",
