diff mbox series

[v3,1/3] kernfs: Convert kernfs_walk_ns() from strlcpy() to strscpy()

Message ID 20231212211741.164376-1-keescook@chromium.org
State New
Headers
Series kernfs: Convert from strlcpy() to strscpy() |

Commit Message

Kees Cook Dec. 12, 2023, 9:17 p.m. UTC 
  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].
Additionally, it returns the size of the source string, not the
resulting size of the destination string. In an effort to remove strlcpy()
completely[2], replace strlcpy() here with strscpy().

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
Link: https://github.com/KSPP/linux/issues/89 [2]
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Azeem Shaikh <azeemshaikh38@gmail.com>
Link: https://lore.kernel.org/r/20231116192127.1558276-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/kernfs/dir.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Tejun Heo Dec. 22, 2023, 12:58 a.m. UTC | #1 
On Tue, Dec 12, 2023 at 01:17:38PM -0800, Kees Cook 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].
> Additionally, it returns the size of the source string, not the
> resulting size of the destination string. In an effort to remove strlcpy()
> completely[2], replace strlcpy() here with strscpy().
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
> Link: https://github.com/KSPP/linux/issues/89 [2]
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Azeem Shaikh <azeemshaikh38@gmail.com>
> Link: https://lore.kernel.org/r/20231116192127.1558276-1-keescook@chromium.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.
diff mbox series

Patch

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8b2bd65d70e7..37353901ede1 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -850,16 +850,16 @@  static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
 					  const unsigned char *path,
 					  const void *ns)
 {
-	size_t len;
+	ssize_t len;
 	char *p, *name;
 
 	lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem);
 
 	spin_lock_irq(&kernfs_pr_cont_lock);
 
-	len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
+	len = strscpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
 
-	if (len >= sizeof(kernfs_pr_cont_buf)) {
+	if (len < 0) {
 		spin_unlock_irq(&kernfs_pr_cont_lock);
 		return NULL;
 	}