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bpf: Replace strncpy() with strscpy()

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Using strncpy() on NUL-terminated strings is considered deprecated[1].
Moreover, if the length of 'task->comm' is less than the destination buffer
size, strncpy() will NUL-pad the destination buffer, which is a needless
performance penalty.

Replacing strncpy() with strscpy() fixes all these issues.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220304070408.233658-1-ytcoode@gmail.com
This commit is contained in:
Yuntao Wang 2022-03-04 15:04:08 +08:00 committed by Andrii Nakryiko
parent 9c6e6a80ee
commit 03b9c7fa3f
1 changed files with 2 additions and 7 deletions
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9
kernel/bpf/helpers.c
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@ -225,13 +225,8 @@ BPF_CALL_2(bpf_get_current_comm, char *, buf, u32, size)
if (unlikely(!task))
goto err_clear;
strncpy(buf, task->comm, size);
/* Verifier guarantees that size > 0. For task->comm exceeding
* size, guarantee that buf is %NUL-terminated. Unconditionally
* done here to save the size test.
*/
buf[size - 1] = 0;
/* Verifier guarantees that size > 0 */
strscpy(buf, task->comm, size);
return 0;
err_clear:
memset(buf, 0, size);