| Message ID | 20231212211741.164376-2-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | kernfs: Convert from strlcpy() to strscpy() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Tue, Dec 12, 2023 at 01:17:39PM -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(). > > Nothing actually checks the return value coming from kernfs_name_locked(), > so this has no impact on error paths. The caller hierarchy is: > > kernfs_name_locked() > kernfs_name() > pr_cont_kernfs_name() > return value ignored > cgroup_name() > current_css_set_cg_links_read() > return value ignored > print_page_owner_memcg() > return value ignored > > 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/20231116192127.1558276-2-keescook@chromium.org > Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Tejun Heo <tj@kernel.org> Thanks.
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 37353901ede1..8c0e5442597e 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -54,9 +54,9 @@ static bool kernfs_lockdep(struct kernfs_node *kn) static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen) { if (!kn) - return strlcpy(buf, "(null)", buflen); + return strscpy(buf, "(null)", buflen); - return strlcpy(buf, kn->parent ? kn->name : "/", buflen); + return strscpy(buf, kn->parent ? kn->name : "/", buflen); } /* kernfs_node_depth - compute depth from @from to @to */ @@ -182,12 +182,12 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to, * @buflen: size of @buf * * Copies the name of @kn into @buf of @buflen bytes. The behavior is - * similar to strlcpy(). + * similar to strscpy(). * * Fills buffer with "(null)" if @kn is %NULL. * - * Return: the length of @kn's name and if @buf isn't long enough, - * it's filled up to @buflen-1 and nul terminated. + * Return: the resulting length of @buf. If @buf isn't long enough, + * it's filled up to @buflen-1 and nul terminated, and returns -E2BIG. * * This function can be called from any context. */
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(). Nothing actually checks the return value coming from kernfs_name_locked(), so this has no impact on error paths. The caller hierarchy is: kernfs_name_locked() kernfs_name() pr_cont_kernfs_name() return value ignored cgroup_name() current_css_set_cg_links_read() return value ignored print_page_owner_memcg() return value ignored 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/20231116192127.1558276-2-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/kernfs/dir.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)