bpf: Reject %p% format string in bprintf-like helpers #9202
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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: [email protected]
Fixes: 48cac3f ("bpf: Implement formatted output helpers with bstr_printf")
Signed-off-by: Paul Chaignon <[email protected]>
This patch adds a couple negative test cases with a trailing % at the end of the format string. Signed-off-by: Paul Chaignon <[email protected]>
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Pull request for series with
subject: bpf: Reject %p% format string in bprintf-like helpers
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=976278