[PATCH] bpf: Replace all non-returning strlcpy with strscpy

[PATCH] bpf: Replace all non-returning strlcpy with strscpy

[Azeem Shaikh]

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
---
 kernel/bpf/preload/bpf_preload_kern.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/preload/bpf_preload_kern.c b/kernel/bpf/preload/bpf_preload_kern.c
index b56f9f3314fd..0c63bc2cd895 100644
--- a/kernel/bpf/preload/bpf_preload_kern.c
+++ b/kernel/bpf/preload/bpf_preload_kern.c
@@ -23,9 +23,9 @@ static void free_links_and_skel(void)
 
 static int preload(struct bpf_preload_info *obj)
 {
-	strlcpy(obj[0].link_name, "maps.debug", sizeof(obj[0].link_name));
+	strscpy(obj[0].link_name, "maps.debug", sizeof(obj[0].link_name));
 	obj[0].link = maps_link;
-	strlcpy(obj[1].link_name, "progs.debug", sizeof(obj[1].link_name));
+	strscpy(obj[1].link_name, "progs.debug", sizeof(obj[1].link_name));
 	obj[1].link = progs_link;
 	return 0;
 }

Re: [PATCH] bpf: Replace all non-returning strlcpy with strscpy

[Kees Cook]

On Tue, May 30, 2023 at 03:56:59PM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] bpf: Replace all non-returning strlcpy with strscpy

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Tue, 30 May 2023 15:56:59 +0000 you wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
> 
> [...]

Here is the summary with links:
  - bpf: Replace all non-returning strlcpy with strscpy
    https://git.kernel.org/bpf/bpf-next/c/ffadc372529e

You are awesome, thank you!
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