[ Upstream commit f824274587 ]
static const char fmt[] = "%p%";
bpf_trace_printk(fmt, sizeof(fmt));
The above BPF program isn't rejected and causes a kernel warning at
runtime:
Please remove unsupported %\x00 in format string
WARNING: CPU: 1 PID: 7244 at lib/vsprintf.c:2680 format_decode+0x49c/0x5d0
This happens because bpf_bprintf_prepare skips over the second %,
detected as punctuation, while processing %p. This patch fixes it by
not skipping over punctuation. %\x00 is then processed in the next
iteration and rejected.
Reported-by: syzbot+e2c932aec5c8a6e1d31c@syzkaller.appspotmail.com
Fixes: 48cac3f4a9 ("bpf: Implement formatted output helpers with bstr_printf")
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/a0e06cc479faec9e802ae51ba5d66420523251ee.1751395489.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
61d5fa45ed