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[PATCH 4.4 44/49] ext4: check for extents that wrap around

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vegard Nossum <vegard.nossum@oracle.com>

commit f70749ca42943faa4d4dcce46dfdcaadb1d0c4b6 upstream.

An extent with lblock = 4294967295 and len = 1 will pass the
ext4_valid_extent() test:

	ext4_lblk_t last = lblock + len - 1;

	if (len == 0 || lblock > last)
		return 0;

since last = 4294967295 + 1 - 1 = 4294967295. This would later trigger
the BUG_ON(es->es_lblk + es->es_len < es->es_lblk) in ext4_es_end().

We can simplify it by removing the - 1 altogether and changing the test
to use lblock + len <= lblock, since now if len = 0, then lblock + 0 ==
lblock and it fails, and if len > 0 then lblock + len > lblock in order
to pass (i.e. it doesn't overflow).

Fixes: 5946d0893 ("ext4: check for overlapping extents in ext4_valid_extent_entries()")
Fixes: 2f974865f ("ext4: check for zero length extent explicitly")
Cc: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/extents.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -376,9 +376,13 @@ static int ext4_valid_extent(struct inod
 	ext4_fsblk_t block = ext4_ext_pblock(ext);
 	int len = ext4_ext_get_actual_len(ext);
 	ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);
-	ext4_lblk_t last = lblock + len - 1;
 
-	if (len == 0 || lblock > last)
+	/*
+	 * We allow neither:
+	 *  - zero length
+	 *  - overflow/wrap-around
+	 */
+	if (lblock + len <= lblock)
 		return 0;
 	return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);
 }

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[PATCH 4.4 00/49] 4.4.18-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 33/49] mm: memcontrol: fix swap counter leak on swapout from offline cgroup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 05/49] net: bgmac: Fix infinite loop in bgmac_dma_tx_add() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 26/49] x86/mtrr: Fix Xorg crashes in Qemu sessions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 28/49] x86/xen, pat: Remove PAT table init code from Xen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 01/49] tcp: make challenge acks less predictable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 03/49] ipv4: reject RTNH_F_DEAD and RTNH_F_LINKDOWN from user space Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 12/49] PNP: Add Broadwell to Intel MCH size workaround Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 23/49] x86/mm/pat: Add support of non-default PAT MSR setting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 24/49] x86/mm/pat: Add pat_disable() interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 10/49] scsi: ignore errors from scsi_dh_add_device() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 20/49] apparmor: fix ref count leak when profile sha1 hash is read Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 41/49] fs/dcache.c: avoid soft-lockup in dput() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 49/49] ext4: fix reference counting bug on block allocation error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 07/49] qed: Fix setting/clearing bit in completion bitmap Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 38/49] fuse: fsync() did not return IO errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 46/49] ext4: dont call ext4_should_journal_data() on the journal inode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 43/49] crypto: scatterwalk - Fix test in scatterwalk_done Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 19/49] Revert "s390/kdump: Clear subchannel ID to signal non-CCW/SCSI IPL" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 45/49] ext4: fix deadlock during page writeback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 22/49] devpts: clean up interface to pty drivers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 48/49] ext4: short-cut orphan cleanup on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 32/49] mm: memcontrol: fix cgroup creation failure after many small jobs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 06/49] net/irda: fix NULL pointer dereference on memory allocation failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 27/49] x86/mtrr: Fix PAT init handling when MTRR is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 44/49] ext4: check for extents that wrap around Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 29/49] x86/pat: Document the PAT initialization sequence Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 36/49] block: fix use-after-free in seq file Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 37/49] sysv, ipc: fix security-layer leaking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 09/49] ipath: Restrict use of the write() interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 35/49] x86/syscalls/64: Add compat_sys_keyctl for 32-bit userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 21/49] random: strengthen input validation for RNDADDTOENTCNT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 04/49] bonding: set carrier off for devices created through netlink Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 11/49] PNP: Add Haswell-ULT to Intel MCH size workaround Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  Re: [PATCH 4.4 00/49] 4.4.18-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-15 10:00 +0200
  Re: [PATCH 4.4 00/49] 4.4.18-stable review Guenter Roeck <linux@roeck-us.net> - 2016-08-15 15:10 +0200
  Re: [PATCH 4.4 00/49] 4.4.18-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-08-16 06:10 +0200

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