diff options
| author | Yonghong Song <yhs@fb.com> | 2020-05-28 17:48:10 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-06-01 14:48:31 -0700 |
| commit | b36e62eb85215a60916f910070f6d494b4f3e73a (patch) | |
| tree | fe2877fddbe43d1430761ecbf07d4b3104a9f433 /kernel/trace | |
| parent | c3c16f2ea6d20159903cf93afbb1155f3d8348d5 (diff) | |
bpf: Use strncpy_from_unsafe_strict() in bpf_seq_printf() helper
In bpf_seq_printf() helper, when user specified a "%s" in the
format string, strncpy_from_unsafe() is used to read the actual string
to a buffer. The string could be a format string or a string in
the kernel data structure. It is really unlikely that the string
will reside in the user memory.
This is different from Commit b2a5212fb634 ("bpf: Restrict bpf_trace_printk()'s %s
usage and add %pks, %pus specifier") which still used
strncpy_from_unsafe() for "%s" to preserve the old behavior.
If in the future, bpf_seq_printf() indeed needs to read user
memory, we can implement "%pus" format string.
Based on discussion in [1], if the intent is to read kernel memory,
strncpy_from_unsafe_strict() should be used. So this patch
changed to use strncpy_from_unsafe_strict().
[1]: https://lore.kernel.org/bpf/20200521152301.2587579-1-hch@lst.de/T/
Fixes: 492e639f0c22 ("bpf: Add bpf_seq_printf and bpf_seq_write helpers")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/bpf/20200529004810.3352219-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 3767d34114c0..b6c24be5ff53 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -585,9 +585,9 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size, goto out; } - err = strncpy_from_unsafe(bufs->buf[memcpy_cnt], - (void *) (long) args[fmt_cnt], - MAX_SEQ_PRINTF_STR_LEN); + err = strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt], + (void *) (long) args[fmt_cnt], + MAX_SEQ_PRINTF_STR_LEN); if (err < 0) bufs->buf[memcpy_cnt][0] = '\0'; params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt]; |