general protection fault in sg_remove_scat

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d63fdf61 Merge 4.4.120 into android-4.4
git tree: android-4.4
console output: https://syzkaller.appspot.com/x/log.txt?x=12cb344b800000
kernel config: https://syzkaller.appspot.com/x/.config?x=b36b3c05dfb8e06d
dashboard link: https://syzkaller.appspot.com/bug?extid=5435e435fc90041aac56
compiler: gcc (GCC) 7.1.1 20170620
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16bbd3cb800000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1198b1e3800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5435e4...@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral
protection fault: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3813 Comm: syzkaller127191 Not tainted 4.4.120-gd63fdf6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff8801c4cd3000 task.stack: ffff8801c4d60000
RIP: 0010:[<ffffffff825b85cb>] [<ffffffff825b85cb>]
sg_remove_scat.isra.17+0x17b/0x2d0 drivers/scsi/sg.c:1949
RSP: 0018:ffff8801c4d67b20 EFLAGS: 00010202
RAX: 1ffff1003878702d RBX: ffff8801c3c38158 RCX: 0000000000000001
RDX: 0000000000000008 RSI: 0000000000000000 RDI: ffff8801d4948874
RBP: ffff8801c4d67b70 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff100389acf3e R12: 0000000000000001
R13: 0000000000000008 R14: 0000000000000000 R15: dffffc0000000000
FS: 00007f736510f700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000045a470 CR3: 00000001d1d36000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
ffff8801c3c38170 ffffed003878702b ffffed003878702e ffff8801c3c38168
ffff8801d4948858 ffff8801c3c38140 0000000000000000 0000000000000000
0000000000000000 ffff8801c3c38238 ffff8801c4d67bb0 ffffffff825b89d5
Call Trace:
[<ffffffff825b89d5>] sg_finish_rem_req+0x2b5/0x340 drivers/scsi/sg.c:1835
[<ffffffff825ba85b>] sg_read+0xa1b/0x1490 drivers/scsi/sg.c:537
[<ffffffff8151cf33>] __vfs_read+0x103/0x440 fs/read_write.c:432
[<ffffffff8151edd3>] vfs_read+0x123/0x3a0 fs/read_write.c:454
[<ffffffff81521719>] SYSC_read fs/read_write.c:569 [inline]
[<ffffffff81521719>] SyS_read+0xd9/0x1b0 fs/read_write.c:562
[<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98
Code: 45 b8 eb 3e e8 a7 87 da fe 48 8b 45 c8 48 c1 e8 03 42 80 3c 38 00 0f
85 3a 01 00 00 4c 8b 73 10 4b 8d 14 2e 48 89 d1 48 c1 e9 03 <42> 80 3c 39
00 0f 85 0b 01 00 00 48 8b 12 49 83 c5 08 48 85 d2
RIP [<ffffffff825b85cb>] sg_remove_scat.isra.17+0x17b/0x2d0
drivers/scsi/sg.c:1949
RSP <ffff8801c4d67b20>
---[ end trace 4581fc0daa4f111e ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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