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

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

From: Dmitry Monakhov <dmonak...@openvz.org>


[ Upstream commit 3116a23bb30272d74ea81baf5d0ee23f602dd15b ]

If bio has no data, such as ones from blkdev_issue_flush(),
then we have nothing to protect.

This patch prevent bugon like follows:

kfree_debugcheck: out of range ptr ac1fa1d106742a5ah
kernel BUG at mm/slab.c:2773!
invalid opcode: 0000 [#1] SMP
Modules linked in: bcache
CPU: 0 PID: 4428 Comm: xfs_io Tainted: G        W       
4.11.0-rc4-ext4-00041-g2ef0043-dirty #43
Hardware name: Virtuozzo KVM, BIOS seabios-1.7.5-11.vz7.4 04/01/2014
task: ffff880137786440 task.stack: ffffc90000ba8000
RIP: 0010:kfree_debugcheck+0x25/0x2a
RSP: 0018:ffffc90000babde0 EFLAGS: 00010082
RAX: 0000000000000034 RBX: ac1fa1d106742a5a RCX: 0000000000000007
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88013f3ccb40
RBP: ffffc90000babde8 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000fcb76420 R11: 00000000725172ed R12: 0000000000000282
R13: ffffffff8150e766 R14: ffff88013a145e00 R15: 0000000000000001
FS:  00007fb09384bf40(0000) GS:ffff88013f200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd0172f9e40 CR3: 0000000137fa9000 CR4: 00000000000006f0
Call Trace:
 kfree+0xc8/0x1b3
 bio_integrity_free+0xc3/0x16b
 bio_free+0x25/0x66
 bio_put+0x14/0x26
 blkdev_issue_flush+0x7a/0x85
 blkdev_fsync+0x35/0x42
 vfs_fsync_range+0x8e/0x9f
 vfs_fsync+0x1c/0x1e
 do_fsync+0x31/0x4a
 SyS_fsync+0x10/0x14
 entry_SYSCALL_64_fastpath+0x1f/0xc2

Reviewed-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Hannes Reinecke <h...@suse.com>
Reviewed-by: Martin K. Petersen <martin.peter...@oracle.com>
Signed-off-by: Dmitry Monakhov <dmonak...@openvz.org>
Signed-off-by: Jens Axboe <ax...@fb.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 block/bio-integrity.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -175,6 +175,9 @@ bool bio_integrity_enabled(struct bio *b
        if (!bio_is_rw(bio))
                return false;
 
+       if (!bio_sectors(bio))
+               return false;
+
        /* Already protected? */
        if (bio_integrity(bio))
                return false;


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