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authorRichard Wareing <rwareing@fb.com>2017-09-13 09:09:35 +1000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-13 14:03:47 -0700
commitb766f0849a52e235268f362b7d8ec8bc36cdc7f0 (patch)
parent43d51814b7b3d57fbf7bac41f1f495adca6cd7f9 (diff)
xfs: XFS_IS_REALTIME_INODE() should be false if no rt device present
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@fb.com> Signed-off-by: Dave Chinner <david@fromorbit.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/xfs/libxfs/xfs_dinode.h b/fs/xfs/libxfs/xfs_dinode.h
index 623bbe8fd921..a62b36731775 100644
--- a/fs/xfs/libxfs/xfs_dinode.h
+++ b/fs/xfs/libxfs/xfs_dinode.h
@@ -228,7 +228,14 @@ static inline void xfs_dinode_put_rdev(struct xfs_dinode *dip, xfs_dev_t rdev)
-#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)
#define XFS_IS_REALTIME_INODE(ip) (0)