BUG: unable to handle kernel paging request in syscall_return_slowpath

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    f66ed1eb Merge tag 'iomap-5.7-fixes-1' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=140f6e60100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1ac152749c11ca54
dashboard link: https://syzkaller.appspot.com/bug?extid=3231e7d48f1538976553
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1415e23fe00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=146bbc3fe00000

Bisection is inconclusive: the bug happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12955ee4100000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=11955ee4100000
console output: https://syzkaller.appspot.com/x/log.txt?x=16955ee4100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3231e7d48f1538976553@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: fffffffff8778570
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 927c067 P4D 927c067 PUD 927e067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 7070 Comm: syz-executor231 Not tainted 5.7.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0xfffffffff8778570
Code: Bad RIP value.
RSP: 0018:ffffc90001627f00 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 0000000000004000 RCX: ffff888092d64280
RDX: ffff888092d64280 RSI: 0000000000000200 RDI: 0000000000000000
RBP: 0000000000000200 R08: ffffffff8100848d R09: fffffbfff16e6e11
R10: fffffbfff16e6e11 R11: 0000000000000000 R12: 1ffff110125ac850
R13: dffffc0000000000 R14: ffff888092d64280 R15: ffff888092d64280
FS:  0000000001be0880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffff8778546 CR3: 00000000a82d6000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 syscall_return_slowpath+0x9b/0x420 arch/x86/entry/common.c:266
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
Modules linked in:
CR2: fffffffff8778570
---[ end trace 8e914c2fec746223 ]---
RIP: 0010:0xfffffffff8778570
Code: Bad RIP value.
RSP: 0018:ffffc90001627f00 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 0000000000004000 RCX: ffff888092d64280
RDX: ffff888092d64280 RSI: 0000000000000200 RDI: 0000000000000000
RBP: 0000000000000200 R08: ffffffff8100848d R09: fffffbfff16e6e11
R10: fffffbfff16e6e11 R11: 0000000000000000 R12: 1ffff110125ac850
R13: dffffc0000000000 R14: ffff888092d64280 R15: ffff888092d64280
FS:  0000000001be0880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffff8778546 CR3: 00000000a82d6000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
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