On 4/9/24 4:37 AM, Edward Adam Davis wrote:
According to the context in bpf_bprintf_prepare(), this is checking if fmt ends
with a NUL word. Therefore, strnchrnul() should be used for validation instead
of strnchr().
As your another email, this is not fixing the uninit KMSAN report.
If there was a separate bug, please post a separate patch instead of replying to
an unrelated thread and confuse syzbot.
Reported-by: syzbot+9b8be5e35747291236c8@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
kernel/bpf/helpers.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 449b9a5d3fe3..07490eba24fe 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -826,7 +826,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
u64 cur_arg;
char fmt_ptype, cur_ip[16], ip_spec[] = "%pXX";
- fmt_end = strnchr(fmt, fmt_size, 0);
+ fmt_end = strnchrnul(fmt, fmt_size, 0);
I don't think it is correct either.
if (!fmt_end)
e.g. what will strnchrnul return if fmt is not NULL terminated?
The current code is correct as is. Comment snippet from strnchr:
/*
* ...
*
* Note that the %NUL-terminator is considered part of the string, and can
* be searched for.
*/
char *strnchr(const char *s, size_t count, int c)
return -EINVAL;
fmt_size = fmt_end - fmt;
