strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.
In xfs_ioctl.c:
The current code has taken care NUL-termination by memset()'ing @label.
This is followed by a strncpy() to perform the string copy.
Use strscpy_pad() to get both 1) NUL-termination and 2) NUL-padding
which may be needed as this is copied out to userspace.
Note that this patch uses the new 2-argument version of strscpy_pad
introduced in Commit e6584c3964f2f ("string: Allow 2-argument
strscpy()").
In xfs_xattr.c:
There's a lot of manual memory management to get a prefix and name into
a string. Let's use an easier to understand and more robust interface in
scnprintf() to accomplish the same task.
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@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
fs/xfs/xfs_ioctl.c | 4 +---
fs/xfs/xfs_xattr.c | 6 +-----
2 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index d0e2cec6210d..abef9707a433 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1755,10 +1755,8 @@ xfs_ioc_getlabel(
/* 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);
+ strscpy_pad(label, sbp->sb_fname);
spin_unlock(&mp->m_sb_lock);
if (copy_to_user(user_label, label, sizeof(label)))
diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
index 364104e1b38a..b9256988830f 100644
--- a/fs/xfs/xfs_xattr.c
+++ b/fs/xfs/xfs_xattr.c
@@ -220,11 +220,7 @@ __xfs_xattr_put_listent(
return;
}
offset = context->buffer + context->count;
- memcpy(offset, prefix, prefix_len);
- offset += prefix_len;
- strncpy(offset, (char *)name, namelen); /* real name */
- offset += namelen;
- *offset = '\0';
+ scnprintf(offset, prefix_len + namelen + 1, "%s%s", prefix, name);
compute_size:
context->count += prefix_len + namelen + 1;
---
base-commit: 928a87efa42302a23bb9554be081a28058495f22
change-id: 20240401-strncpy-fs-xfs-xfs_ioctl-c-8af7a895bff0
Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>
