[syzbot] WARNING in scsi_alloc_sgtables

[syzbot <syzbot+d44b35ecfb807e5af0b5@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    dd9c7df94c1b Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13dffb78300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4743a765b066cc1c
dashboard link: https://syzkaller.appspot.com/bug?extid=d44b35ecfb807e5af0b5

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+d44b35ecfb807e5af0b5@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 15940 at drivers/scsi/scsi_lib.c:988 scsi_alloc_sgtables+0xc92/0xf80 drivers/scsi/scsi_lib.c:988
Modules linked in:
CPU: 1 PID: 15940 Comm: syz-executor.0 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:scsi_alloc_sgtables+0xc92/0xf80 drivers/scsi/scsi_lib.c:988
Code: 31 ff 44 89 f6 e8 1e e5 f3 fc 45 85 f6 0f 84 28 f5 ff ff e8 60 dc f3 fc 41 83 c4 01 45 0f b7 e4 e9 1b f5 ff ff e8 4e dc f3 fc <0f> 0b 41 be 0a 00 00 00 e9 25 fb ff ff 41 be 09 00 00 00 e9 1a fb
RSP: 0018:ffffc90003c87468 EFLAGS: 00010202
RAX: 00000000000086f0 RBX: ffff88801d2c0128 RCX: ffffc90001929000
RDX: 0000000000040000 RSI: ffffffff8480e152 RDI: 0000000000000003
RBP: ffff88801d2c0000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff8480d659 R11: 0000000000000000 R12: 0000000000000000
R13: ffff888014892000 R14: 0000000000000000 R15: ffff888014448000
FS:  00007f47d4121700(0000) GS:ffff88802cb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000515cb0 CR3: 000000004d420000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 scsi_setup_scsi_cmnd drivers/scsi/scsi_lib.c:1160 [inline]
 scsi_prepare_cmd drivers/scsi/scsi_lib.c:1559 [inline]
 scsi_queue_rq+0x26b2/0x35b0 drivers/scsi/scsi_lib.c:1665
 blk_mq_dispatch_rq_list+0x422/0x1f00 block/blk-mq.c:1380
 __blk_mq_sched_dispatch_requests+0x20b/0x410 block/blk-mq-sched.c:327
 blk_mq_sched_dispatch_requests+0xfb/0x180 block/blk-mq-sched.c:360
 __blk_mq_run_hw_queue+0xd8/0x150 block/blk-mq.c:1500
 __blk_mq_delay_run_hw_queue+0x547/0x640 block/blk-mq.c:1577
 blk_mq_run_hw_queue+0x16c/0x2f0 block/blk-mq.c:1630
 blk_mq_sched_insert_request+0x368/0x450 block/blk-mq-sched.c:479
 blk_execute_rq+0xdc/0x410 block/blk-exec.c:96
 sg_io+0x602/0xfe0 block/scsi_ioctl.c:358
 scsi_cmd_ioctl+0x519/0x580 block/scsi_ioctl.c:808
 scsi_cmd_blk_ioctl block/scsi_ioctl.c:866 [inline]
 scsi_cmd_blk_ioctl+0xe1/0x130 block/scsi_ioctl.c:857
 sd_ioctl_common+0x17e/0x280 drivers/scsi/sd.c:1585
 sd_ioctl+0x26/0xf0 drivers/scsi/sd.c:1778
 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:585
 block_ioctl+0xf9/0x140 fs/block_dev.c:1602
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:1069 [inline]
 __se_sys_ioctl fs/ioctl.c:1055 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f47d4121188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 00000000200065c0 RSI: 0000000000002285 RDI: 0000000000000004
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffc92ec284f R14: 00007f47d4121300 R15: 0000000000022000


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