From: Justin Stitt <justinstitt@google.com>
To: Chandan Babu R <chandan.babu@oracle.com>,
"Darrick J. Wong" <djwong@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org,
Justin Stitt <justinstitt@google.com>
Subject: [PATCH v2] xfs: replace deprecated strncpy with memtostr_pad
Date: Wed, 10 Apr 2024 20:43:33 +0000 [thread overview]
Message-ID: <20240410-strncpy-xfs-split1-v2-1-7c651502bcb0@google.com> (raw)
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(-)
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index d0e2cec6210d..7ed7a5d57094 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -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)))
---
base-commit: c85af715cac0a951eea97393378e84bb49384734
change-id: 20240405-strncpy-xfs-split1-a2c408b934c6
Best regards,
--
Justin Stitt <justinstitt@google.com>
reply other threads:[~2024-04-10 20:43 UTC|newest]
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