general protection fault in dma_buf_release

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    9e50b94b Add linux-next specific files for 20200703
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=121cf755100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f99cc0faa1476ed6
dashboard link: https://syzkaller.appspot.com/bug?extid=4342719956b367864c91
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1467c5e3100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=153f2283100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4342719956b367864c91@xxxxxxxxxxxxxxxxxxxxxxxxx

RBP: 00000000000103d6 R08: 0000000000000001 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402170
R13: 0000000000402200 R14: 0000000000000000 R15: 0000000000000000
general protection fault, probably for non-canonical address 0xdffffc0000000017: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000b8-0x00000000000000bf]
CPU: 1 PID: 6798 Comm: syz-executor223 Not tainted 5.8.0-rc3-next-20200703-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:dma_buf_release+0x51/0x3f0 drivers/dma-buf/dma-buf.c:63
Code: 03 80 3c 02 00 0f 85 30 03 00 00 48 8b ad e8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d bd b8 00 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e e3 02 00 00 8b 9d b8 00 00 00
RSP: 0018:ffffc90001b87aa0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffffffff847e30a0 RCX: ffffffff81c58a83
RDX: 0000000000000017 RSI: ffffffff847e30b0 RDI: 00000000000000b8
RBP: 0000000000000000 R08: 0000000000000001 R09: ffff88808a53c80b
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88808b7dc550
R13: ffff88808b7dc4d8 R14: ffff88808b7dc520 R15: 0000000000000000
FS:  0000000001f09880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cc090 CR3: 00000000a87d2000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __dentry_kill+0x42b/0x640 fs/dcache.c:584
 dentry_kill fs/dcache.c:705 [inline]
 dput+0x725/0xbc0 fs/dcache.c:878
 path_put+0x2d/0x60 fs/namei.c:496
 alloc_file_pseudo+0x20d/0x250 fs/file_table.c:236
 dma_buf_getfile drivers/dma-buf/dma-buf.c:439 [inline]
 dma_buf_export+0x5d8/0xae0 drivers/dma-buf/dma-buf.c:555
 udmabuf_create+0xb9d/0xe30 drivers/dma-buf/udmabuf.c:228
 udmabuf_ioctl_create_list drivers/dma-buf/udmabuf.c:284 [inline]
 udmabuf_ioctl+0x265/0x2c0 drivers/dma-buf/udmabuf.c:299
 vfs_ioctl fs/ioctl.c:48 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:753
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl fs/ioctl.c:760 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:760
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:367
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x441229
Code: Bad RIP value.
RSP: 002b:00007ffe24394848 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441229
RDX: 0000000020000000 RSI: 0000000040087543 RDI: 0000000000000004
RBP: 00000000000103d6 R08: 0000000000000001 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402170
R13: 0000000000402200 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 1a68562902844a66 ]---
RIP: 0010:dma_buf_release+0x51/0x3f0 drivers/dma-buf/dma-buf.c:63
Code: 03 80 3c 02 00 0f 85 30 03 00 00 48 8b ad e8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d bd b8 00 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e e3 02 00 00 8b 9d b8 00 00 00
RSP: 0018:ffffc90001b87aa0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffffffff847e30a0 RCX: ffffffff81c58a83
RDX: 0000000000000017 RSI: ffffffff847e30b0 RDI: 00000000000000b8
RBP: 0000000000000000 R08: 0000000000000001 R09: ffff88808a53c80b
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88808b7dc550
R13: ffff88808b7dc4d8 R14: ffff88808b7dc520 R15: 0000000000000000
FS:  0000000001f09880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cc090 CR3: 00000000a87d2000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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