KASAN: use-after-free Read in recv_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    b01f250d Add linux-next specific files for 20210129
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14366378d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=725bc96dc234fda7
dashboard link: https://syzkaller.appspot.com/bug?extid=f91dbbabacae745d334f
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f91dbbabacae745d334f@xxxxxxxxxxxxxxxxxxxxxxxxx

block nbd5: Receive control failed (result -107)
==================================================================
BUG: KASAN: use-after-free in recv_work+0x2a2/0x2c0 drivers/block/nbd.c:787
Read of size 8 at addr ffff88801181ed20 by task kworker/u5:2/8465

CPU: 1 PID: 8465 Comm: kworker/u5:2 Not tainted 5.11.0-rc5-next-20210129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: knbd5-recv recv_work
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
 __kasan_report mm/kasan/report.c:399 [inline]
 kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
 recv_work+0x2a2/0x2c0 drivers/block/nbd.c:787
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Allocated by task 17044:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:403 [inline]
 ____kasan_kmalloc mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc.constprop.0+0xa0/0xd0 mm/kasan/common.c:406
 kasan_slab_alloc include/linux/kasan.h:208 [inline]
 slab_post_alloc_hook mm/slab.h:516 [inline]
 slab_alloc_node mm/slub.c:2907 [inline]
 slab_alloc mm/slub.c:2915 [inline]
 __kmalloc_track_caller+0x16c/0x2e0 mm/slub.c:4550
 __do_krealloc mm/slab_common.c:1149 [inline]
 krealloc+0x60/0xa0 mm/slab_common.c:1178
 nbd_add_socket+0x263/0x6a0 drivers/block/nbd.c:1044
 __nbd_ioctl drivers/block/nbd.c:1369 [inline]
 nbd_ioctl+0x388/0xa50 drivers/block/nbd.c:1425
 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:576
 block_ioctl+0xf9/0x140 fs/block_dev.c:1650
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 17044:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
 ____kasan_slab_free.part.0+0xe1/0x110 mm/kasan/common.c:364
 kasan_slab_free include/linux/kasan.h:191 [inline]
 slab_free_hook mm/slub.c:1562 [inline]
 slab_free_freelist_hook+0x82/0x1d0 mm/slub.c:1600
 slab_free mm/slub.c:3161 [inline]
 kfree+0xe5/0x7b0 mm/slub.c:4202
 krealloc+0x45/0xa0 mm/slab_common.c:1180
 nbd_add_socket+0x263/0x6a0 drivers/block/nbd.c:1044
 __nbd_ioctl drivers/block/nbd.c:1369 [inline]
 nbd_ioctl+0x388/0xa50 drivers/block/nbd.c:1425
 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:576
 block_ioctl+0xf9/0x140 fs/block_dev.c:1650
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88801181ed20
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 8-byte region [ffff88801181ed20, ffff88801181ed28)
The buggy address belongs to the page:
page:00000000e0a0f4b5 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1181e
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffffea000053d180 0000000500000005 ffff88800fc41280
raw: ffff88801181ef28 0000000080660062 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88801181ec00: fc 00 fc fc fc fc fa fc fc fc fc 00 fc fc fc fc
 ffff88801181ec80: fa fc fc fc fc 00 fc fc fc fc 00 fc fc fc fc 00
>ffff88801181ed00: fc fc fc fc fa fc fc fc fc 00 fc fc fc fc 00 fc
                               ^
 ffff88801181ed80: fc fc fc 00 fc fc fc fc 00 fc fc fc fc fa fc fc
 ffff88801181ee00: fc fc 00 fc fc fc fc fa fc fc fc fc 00 fc fc fc
==================================================================


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