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xfs: XFS_IS_REALTIME_INODE() should be false if no rt device present (CVE-2017-14340)

This commit is contained in:
Salvatore Bonaccorso 2017-09-14 06:40:30 +02:00
parent bcc9a01d8e
commit 8f075a9a83
3 changed files with 75 additions and 0 deletions
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2
debian/changelog vendored
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@ -2,6 +2,8 @@ linux (4.12.12-3) UNRELEASED; urgency=medium
* sctp: Avoid out-of-bounds reads from address storage (CVE-2017-7558)
* scsi: qla2xxx: Fix an integer overflow in sysfs code (CVE-2017-14051)
* xfs: XFS_IS_REALTIME_INODE() should be false if no rt device present
(CVE-2017-14340)
-- Salvatore Bonaccorso <carnil@debian.org> Thu, 14 Sep 2017 06:25:04 +0200

72
debian/patches/bugfix/all/xfs-XFS_IS_REALTIME_INODE-should-be-false-if-no-rt-d.patch vendored Normal file
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@ -0,0 +1,72 @@
From: Richard Wareing <rwareing@fb.com>
Date: Wed, 13 Sep 2017 09:09:35 +1000
Subject: xfs: XFS_IS_REALTIME_INODE() should be false if no rt device present
Origin: https://git.kernel.org/linus/b31ff3cdf540110da4572e3e29bd172087af65cc
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-14340
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")
Cc: <stable@vger.kernel.org>
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>
---
fs/xfs/xfs_linux.h | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 9301c5a6060b..dcd1292664b3 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -270,7 +270,14 @@ static inline uint64_t howmany_64(uint64_t x, uint32_t y)
#endif /* DEBUG */
#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
--
2.11.0

1
debian/patches/series vendored
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@ -122,6 +122,7 @@ features/all/lockdown/arm64-add-kernel-config-option-to-lock-down-when.patch
debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
bugfix/all/sctp-Avoid-out-of-bounds-reads-from-address-storage.patch
bugfix/all/scsi-qla2xxx-Fix-an-integer-overflow-in-sysfs-code.patch
bugfix/all/xfs-XFS_IS_REALTIME_INODE-should-be-false-if-no-rt-d.patch
# Fix exported symbol versions
bugfix/alpha/alpha-restore-symbol-versions-for-symbols-exported-f.patch