memory leak in vq_meta_prefetch

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    c6dd78fc Merge branch 'x86-urgent-for-linus' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15fffef4600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8de7d700ea5ac607
dashboard link: https://syzkaller.appspot.com/bug?extid=a871c1e6ea00685e73d7
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=127b0334600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12609e94600000

The bug was bisected to:

commit 0e5f7d0b39e1f184dc25e3adb580c79e85332167
Author: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
Date:   Wed Mar 16 13:19:49 2016 +0000

    ARM: dts: at91: shdwc binding: add new shutdown controller documentation

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16c6d53fa00000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=15c6d53fa00000
console output: https://syzkaller.appspot.com/x/log.txt?x=11c6d53fa00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a871c1e6ea00685e73d7@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 0e5f7d0b39e1 ("ARM: dts: at91: shdwc binding: add new shutdown  
controller documentation")

executing program
executing program
executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff88811b327cc0 (size 32):
  comm "vhost-7201", pid 7205, jiffies 4294952492 (age 19.700s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<000000009e106308>] kmemleak_alloc_recursive  
/./include/linux/kmemleak.h:43 [inline]
    [<000000009e106308>] slab_post_alloc_hook /mm/slab.h:522 [inline]
    [<000000009e106308>] slab_alloc /mm/slab.c:3319 [inline]
    [<000000009e106308>] kmem_cache_alloc_trace+0x145/0x280 /mm/slab.c:3548
    [<00000000ed2eec2d>] kmalloc /./include/linux/slab.h:552 [inline]
    [<00000000ed2eec2d>] vhost_map_prefetch /drivers/vhost/vhost.c:877  
[inline]
    [<00000000ed2eec2d>] vhost_vq_map_prefetch /drivers/vhost/vhost.c:1838  
[inline]
    [<00000000ed2eec2d>] vq_meta_prefetch+0x18e/0x350  
/drivers/vhost/vhost.c:1849
    [<000000009d9c11b8>] handle_rx+0x9d/0xc00 /drivers/vhost/net.c:1128
    [<000000008f883d86>] handle_rx_net+0x19/0x20 /drivers/vhost/net.c:1270
    [<00000000577ffdd8>] vhost_worker+0xc6/0x120 /drivers/vhost/vhost.c:519
    [<000000001201f3db>] kthread+0x13e/0x160 /kernel/kthread.c:255
    [<00000000093cd85a>] ret_from_fork+0x1f/0x30  
/arch/x86/entry/entry_64.S:352

BUG: memory leak
unreferenced object 0xffff88811b327cc0 (size 32):
  comm "vhost-7201", pid 7205, jiffies 4294952492 (age 20.600s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<000000009e106308>] kmemleak_alloc_recursive  
/./include/linux/kmemleak.h:43 [inline]
    [<000000009e106308>] slab_post_alloc_hook /mm/slab.h:522 [inline]
    [<000000009e106308>] slab_alloc /mm/slab.c:3319 [inline]
    [<000000009e106308>] kmem_cache_alloc_trace+0x145/0x280 /mm/slab.c:3548
    [<00000000ed2eec2d>] kmalloc /./include/linux/slab.h:552 [inline]
    [<00000000ed2eec2d>] vhost_map_prefetch /drivers/vhost/vhost.c:877  
[inline]
    [<00000000ed2eec2d>] vhost_vq_map_prefetch /drivers/vhost/vhost.c:1838  
[inline]
    [<00000000ed2eec2d>] vq_meta_prefetch+0x18e/0x350  
/drivers/vhost/vhost.c:1849
    [<000000009d9c11b8>] handle_rx+0x9d/0xc00 /drivers/vhost/net.c:1128
    [<000000008f883d86>] handle_rx_net+0x19/0x20 /drivers/vhost/net.c:1270
    [<00000000577ffdd8>] vhost_worker+0xc6/0x120 /drivers/vhost/vhost.c:519
    [<000000001201f3db>] kthread+0x13e/0x160 /kernel/kthread.c:255
    [<00000000093cd85a>] ret_from_fork+0x1f/0x30  
/arch/x86/entry/entry_64.S:352



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