Using strncpy() on NUL-terminated strings is considered deprecated[1],
replace it with strscpy_pad().
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Signed-off-by: Yuntao Wang <[email protected]>
---
kernel/bpf/helpers.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index ae64110a98b5..d03b28761a67 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -225,13 +225,7 @@ 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;
+ strscpy_pad(buf, task->comm, size);
return 0;
err_clear:
memset(buf, 0, size);
--
2.35.1
On 3/3/22 12:18 AM, Yuntao Wang wrote:
> Using strncpy() on NUL-terminated strings is considered deprecated[1],
> replace it with strscpy_pad().
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
>
> Signed-off-by: Yuntao Wang <[email protected]>
> ---
> kernel/bpf/helpers.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index ae64110a98b5..d03b28761a67 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -225,13 +225,7 @@ 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;
> + strscpy_pad(buf, task->comm, size);
The precise replacement should be strscpy(...), right?
I am not sure whether we want to do pad here or not, probably
not as it is mostly used by user space for string copy/print
and we don't have cases demanding padding yet.
Please keep the comment
/* Verifier guarantees that size > 0 */
this is important as strscpy will not do anything if size == 0.
> return 0;
> err_clear:
> memset(buf, 0, size);
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 <[email protected]>
---
v1 -> v2: replace strncpy() with strscpy() instead of strscpy_pad()
kernel/bpf/helpers.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index ae64110a98b5..315053ef6a75 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -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);
--
2.35.1
On 3/3/22 11:04 PM, Yuntao Wang wrote:
> 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 <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <[email protected]>:
On Fri, 4 Mar 2022 15:04:08 +0800 you wrote:
> 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.
>
> [...]
Here is the summary with links:
- [bpf-next,v2] bpf: Replace strncpy() with strscpy()
https://git.kernel.org/bpf/bpf-next/c/03b9c7fa3f15
You are awesome, thank you!
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