73 lines
2.5 KiB
Diff
73 lines
2.5 KiB
Diff
From: Richard Wareing <rwareing@fb.com>
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Date: Wed, 13 Sep 2017 09:09:35 +1000
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Subject: xfs: XFS_IS_REALTIME_INODE() should be false if no rt device present
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Origin: https://git.kernel.org/linus/b31ff3cdf540110da4572e3e29bd172087af65cc
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-14340
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If using a kernel with CONFIG_XFS_RT=y and we set the RHINHERIT flag on
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a directory in a filesystem that does not have a realtime device and
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create a new file in that directory, it gets marked as a real time file.
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When data is written and a fsync is issued, the filesystem attempts to
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flush a non-existent rt device during the fsync process.
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This results in a crash dereferencing a null buftarg pointer in
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xfs_blkdev_issue_flush():
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BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
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IP: xfs_blkdev_issue_flush+0xd/0x20
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.....
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Call Trace:
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xfs_file_fsync+0x188/0x1c0
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vfs_fsync_range+0x3b/0xa0
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do_fsync+0x3d/0x70
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SyS_fsync+0x10/0x20
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do_syscall_64+0x4d/0xb0
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entry_SYSCALL64_slow_path+0x25/0x25
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Setting RT inode flags does not require special privileges so any
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unprivileged user can cause this oops to occur. To reproduce, confirm
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kernel is compiled with CONFIG_XFS_RT=y and run:
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# mkfs.xfs -f /dev/pmem0
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# mount /dev/pmem0 /mnt/test
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# mkdir /mnt/test/foo
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# xfs_io -c 'chattr +t' /mnt/test/foo
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# xfs_io -f -c 'pwrite 0 5m' -c fsync /mnt/test/foo/bar
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Or just run xfstests with MKFS_OPTIONS="-d rtinherit=1" and wait.
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Kernels built with CONFIG_XFS_RT=n are not exposed to this bug.
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Fixes: f538d4da8d52 ("[XFS] write barrier support")
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Cc: <stable@vger.kernel.org>
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Signed-off-by: Richard Wareing <rwareing@fb.com>
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Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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fs/xfs/xfs_linux.h | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
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index 9301c5a6060b..dcd1292664b3 100644
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--- a/fs/xfs/xfs_linux.h
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+++ b/fs/xfs/xfs_linux.h
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@@ -270,7 +270,14 @@ static inline uint64_t howmany_64(uint64_t x, uint32_t y)
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#endif /* DEBUG */
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#ifdef CONFIG_XFS_RT
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-#define XFS_IS_REALTIME_INODE(ip) ((ip)->i_d.di_flags & XFS_DIFLAG_REALTIME)
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+
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+/*
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+ * make sure we ignore the inode flag if the filesystem doesn't have a
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+ * configured realtime device.
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+ */
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+#define XFS_IS_REALTIME_INODE(ip) \
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+ (((ip)->i_d.di_flags & XFS_DIFLAG_REALTIME) && \
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+ (ip)->i_mount->m_rtdev_targp)
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#else
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#define XFS_IS_REALTIME_INODE(ip) (0)
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#endif
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--
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2.11.0
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