@@ -1750,15 +1750,14 @@ xfs_ioc_getlabel(
char __user *user_label)
{
struct xfs_sb *sbp = &mp->m_sb;
+ /* 1 larger than sb_fname, for a NULL byte */
char label[XFSLABEL_MAX + 1];
/* Paranoia */
BUILD_BUG_ON(sizeof(sbp->sb_fname) > FSLABEL_MAX);
- /* 1 larger than sb_fname, so this ensures a trailing NUL char */
- memset(label, 0, sizeof(label));
spin_lock(&mp->m_sb_lock);
- strncpy(label, sbp->sb_fname, XFSLABEL_MAX);
+ memtostr_pad(label, sbp->sb_fname);
spin_unlock(&mp->m_sb_lock);
if (copy_to_user(user_label, label, sizeof(label)))
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. sbp->sb_fname may not be NUL-terminated while label is expected to be. memtostr best describes this behavior, specifically, use the pad variant since we're copying out to userspace. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Changes in v2: - use memtostr_pad (thanks Kees) - Link to v1: https://lore.kernel.org/r/20240405-strncpy-xfs-split1-v1-1-3e3df465adb9@google.com --- Note: This patch relies on the memtostr{_pad} implementation from Kees' patch: https://lore.kernel.org/all/20240410023155.2100422-1-keescook@chromium.org/ Split from https://lore.kernel.org/all/20240401-strncpy-fs-xfs-xfs_ioctl-c-v1-1-02b9feb1989b@google.com/ with feedback from Christoph H. --- fs/xfs/xfs_ioctl.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- base-commit: c85af715cac0a951eea97393378e84bb49384734 change-id: 20240405-strncpy-xfs-split1-a2c408b934c6 Best regards, -- Justin Stitt <justinstitt@google.com>