BUG: unable to handle kernel NULL pointer dereference in read_pages

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a55aa89a Linux 5.3-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10a5d212600000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
dashboard link: https://syzkaller.appspot.com/bug?extid=10533fbe9a7c8d87cef9
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [ak...@linux-foundation.org amir...@gmail.com
hsia...@aol.com jba...@fb.com linux-...@vger.kernel.org
linu...@kvack.org rp...@linux.ibm.com tg...@linutronix.de
wi...@infradead.org]

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+10533f...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 91cec067 P4D 91cec067 PUD 8a8b2067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 19282 Comm: syz-executor.1 Not tainted 5.3.0-rc6 #127
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:0x0
Code: Bad RIP value.
RSP: 0018:ffff88805b6b75b8 EFLAGS: 00010246
RAX: ffffffff879c54c0 RBX: dffffc0000000000 RCX: ffffc9000815e000
RDX: 1ffffffff0f38a99 RSI: ffffea0001cfd640 RDI: ffff888097248500
RBP: ffff88805b6b76e8 R08: ffff8880507c2500 R09: fffff9400039fac9
R10: fffff9400039fac8 R11: ffffea0001cfd647 R12: ffffea0001cfd648
R13: ffffea0001cfd640 R14: ffffea0001cfd650 R15: 0000000000000000
FS: 00007f39fb12c700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000a19e1000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
read_pages+0x352/0x540 mm/readahead.c:136
__do_page_cache_readahead+0x4e0/0x5d0 mm/readahead.c:212
ra_submit mm/internal.h:62 [inline]
ondemand_readahead+0x561/0xd40 mm/readahead.c:492
page_cache_sync_readahead mm/readahead.c:527 [inline]
page_cache_sync_readahead+0x281/0x520 mm/readahead.c:509
generic_file_buffered_read mm/filemap.c:2071 [inline]
generic_file_read_iter+0x10f1/0x1ce0 mm/filemap.c:2344
ext4_file_read_iter fs/ext4/file.c:77 [inline]
ext4_file_read_iter+0x1d6/0x420 fs/ext4/file.c:65
call_read_iter include/linux/fs.h:1864 [inline]
generic_file_splice_read+0x4af/0x800 fs/splice.c:307
do_splice_to+0x127/0x180 fs/splice.c:877
splice_direct_to_actor+0x2d2/0x970 fs/splice.c:954
do_splice_direct+0x1da/0x2a0 fs/splice.c:1063
do_sendfile+0x597/0xd00 fs/read_write.c:1464
__do_sys_sendfile64 fs/read_write.c:1525 [inline]
__se_sys_sendfile64 fs/read_write.c:1511 [inline]
__x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459879
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f39fb12bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459879
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000020000000ffe R11: 0000000000000246 R12: 00007f39fb12c6d4
R13: 00000000004c7065 R14: 00000000004dc6d0 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000000
---[ end trace 0e10cc5a1c1997ea ]---
RIP: 0010:0x0
Code: Bad RIP value.
RSP: 0018:ffff88805b6b75b8 EFLAGS: 00010246
RAX: ffffffff879c54c0 RBX: dffffc0000000000 RCX: ffffc9000815e000
RDX: 1ffffffff0f38a99 RSI: ffffea0001cfd640 RDI: ffff888097248500
RBP: ffff88805b6b76e8 R08: ffff8880507c2500 R09: fffff9400039fac9
R10: fffff9400039fac8 R11: ffffea0001cfd647 R12: ffffea0001cfd648
R13: ffffea0001cfd640 R14: ffffea0001cfd650 R15: 0000000000000000
FS: 00007f39fb12c700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000758080 CR3: 00000000a19e1000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.