| Message ID | 20111021211818.10784.77127.stgit@elm3c44.beaverton.ibm.com |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Fri, Oct 21, 2011 at 02:18:18PM -0700, Darrick J. Wong wrote: > In ext4_file_open, the filesystem records the mountpoint of the first file that > is opened after mounting the filesystem. It does this by allocating a 64-byte > stack buffer, calling d_path() to grab the mount point through which this file > was accessed, and then memcpy()ing 64 bytes into the superblock's > s_last_mounted field, starting from the return value of d_path(), which is > stored as "cp". However, if cp > buf (which it frequently is since path > components are prepended starting at the end of buf) then we can end up copying > stack data into the superblock. > > Writing stack variables into the superblock doesn't sound like a great idea, so > use strlcpy instead. Andi Kleen suggested using strlcpy instead of strncpy. > > Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> Thanks, applied. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/ext4/file.c b/fs/ext4/file.c index e4095e9..9781099 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -181,8 +181,8 @@ static int ext4_file_open(struct inode * inode, struct file * filp) path.dentry = mnt->mnt_root; cp = d_path(&path, buf, sizeof(buf)); if (!IS_ERR(cp)) { - memcpy(sbi->s_es->s_last_mounted, cp, - sizeof(sbi->s_es->s_last_mounted)); + strlcpy(sbi->s_es->s_last_mounted, cp, + sizeof(sbi->s_es->s_last_mounted)); ext4_mark_super_dirty(sb); } }
In ext4_file_open, the filesystem records the mountpoint of the first file that is opened after mounting the filesystem. It does this by allocating a 64-byte stack buffer, calling d_path() to grab the mount point through which this file was accessed, and then memcpy()ing 64 bytes into the superblock's s_last_mounted field, starting from the return value of d_path(), which is stored as "cp". However, if cp > buf (which it frequently is since path components are prepended starting at the end of buf) then we can end up copying stack data into the superblock. Writing stack variables into the superblock doesn't sound like a great idea, so use strlcpy instead. Andi Kleen suggested using strlcpy instead of strncpy. Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> --- fs/ext4/file.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html