Files
linux/kernel
Paul Chaignon f824274587 bpf: Reject %p% format string in bprintf-like helpers
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>
2025-07-01 15:22:46 -07:00
..
2025-06-27 15:51:36 -04:00
2025-02-10 16:56:58 -08:00
2025-05-06 13:59:00 +02:00
2024-11-03 01:28:06 -05:00
2025-02-12 12:12:27 +01:00