Commit 03b9c7fa authored by Yuntao Wang's avatar Yuntao Wang Committed by Andrii Nakryiko
Browse files

bpf: Replace strncpy() with strscpy() 

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: default avatarYuntao Wang <ytcoode@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220304070408.233658-1-ytcoode@gmail.com
parent 9c6e6a80

kernel/bpf/helpers.c

+2 −7
Original line number Diff line number Diff line
@@ -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);