From: Camila Alvarez <cam.alvarez.i@gmail.com>
To: ast@kernel.org, daniel@iogearbox.net
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Camila Alvarez <cam.alvarez.i@gmail.com>,
syzbot+d2a2c639d03ac200a4f1@syzkaller.appspotmail.com
Subject: [PATCH] fix array-index-out-of-bounds in bpf_prog_select_runtime
Date: Sat, 4 May 2024 21:46:43 -0400 [thread overview]
Message-ID: <20240505014641.203643-1-cam.alvarez.i@gmail.com> (raw)
The error indicates that the verifier is letting through a program with
a stack depth bigger than 512.
This is due to the verifier not checking the stack depth after
instruction rewrites are perfomed. For example, the MAY_GOTO instruction
adds 8 bytes to the stack, which means that if the stack at the moment
was already 512 bytes it would overflow after rewriting the instruction.
The fix involves adding a stack depth check after all instruction
rewrites are performed.
Reported-by: syzbot+d2a2c639d03ac200a4f1@syzkaller.appspotmail.com
Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
---
kernel/bpf/verifier.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 63749ad5ac6b..a9e23b6b8e8f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -21285,6 +21285,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
if (ret == 0)
ret = do_misc_fixups(env);
+ /* max stack depth verification must be done after rewrites as well */
+ if (ret == 0)
+ ret = check_max_stack_depth(env);
+
/* do 32-bit optimization after insn patching has done so those patched
* insns could be handled correctly.
*/
--
2.34.1
next reply other threads:[~2024-05-05 1:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-05 1:46 Camila Alvarez [this message]
2024-05-05 8:21 ` [PATCH] fix array-index-out-of-bounds in bpf_prog_select_runtime Alexei Starovoitov
2024-05-05 23:18 ` Camila Alvarez Inostroza
2024-05-06 23:35 ` Alexei Starovoitov
-- strict thread matches above, loose matches on Subject: below --
2024-03-26 0:38 Camila Alvarez
2024-03-27 22:14 ` Alexei Starovoitov
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