3.2.94-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Richard Wareing <rwareing@xxxxxx>
commit b31ff3cdf540110da4572e3e29bd172087af65cc upstream.
If using a kernel with CONFIG_XFS_RT=y and we set the RHINHERIT flag on
a directory in a filesystem that does not have a realtime device and
create a new file in that directory, it gets marked as a real time file.
When data is written and a fsync is issued, the filesystem attempts to
flush a non-existent rt device during the fsync process.
This results in a crash dereferencing a null buftarg pointer in
xfs_blkdev_issue_flush():
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: xfs_blkdev_issue_flush+0xd/0x20
.....
Call Trace:
xfs_file_fsync+0x188/0x1c0
vfs_fsync_range+0x3b/0xa0
do_fsync+0x3d/0x70
SyS_fsync+0x10/0x20
do_syscall_64+0x4d/0xb0
entry_SYSCALL64_slow_path+0x25/0x25
Setting RT inode flags does not require special privileges so any
unprivileged user can cause this oops to occur. To reproduce, confirm
kernel is compiled with CONFIG_XFS_RT=y and run:
# mkfs.xfs -f /dev/pmem0
# mount /dev/pmem0 /mnt/test
# mkdir /mnt/test/foo
# xfs_io -c 'chattr +t' /mnt/test/foo
# xfs_io -f -c 'pwrite 0 5m' -c fsync /mnt/test/foo/bar
Or just run xfstests with MKFS_OPTIONS="-d rtinherit=1" and wait.
Kernels built with CONFIG_XFS_RT=n are not exposed to this bug.
Fixes: f538d4da8d52 ("[XFS] write barrier support")
Signed-off-by: Richard Wareing <rwareing@xxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
fs/xfs/xfs_dinode.h | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/fs/xfs/xfs_dinode.h
+++ b/fs/xfs/xfs_dinode.h
@@ -201,7 +201,14 @@ static inline void xfs_dinode_put_rdev(s
#define XFS_DIFLAG_FILESTREAM (1 << XFS_DIFLAG_FILESTREAM_BIT)
#ifdef CONFIG_XFS_RT
-#define XFS_IS_REALTIME_INODE(ip) ((ip)->i_d.di_flags & XFS_DIFLAG_REALTIME)
+
+/*
+ * make sure we ignore the inode flag if the filesystem doesn't have a
+ * configured realtime device.
+ */
+#define XFS_IS_REALTIME_INODE(ip) \
+ (((ip)->i_d.di_flags & XFS_DIFLAG_REALTIME) && \
+ (ip)->i_mount->m_rtdev_targp)
#else
#define XFS_IS_REALTIME_INODE(ip) (0)
#endif