[moderation] [fs?] general protection fault in mpage_readahead

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 262858079afd Add linux-next specific files for 20250926
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13128ae2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6117d7eea7e1f3a7
dashboard link: https://syzkaller.appspot.com/bug?extid=31c428684be9035d5108
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/818c8ba6ac53/disk-26285807.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/da143e1d7f10/vmlinux-26285807.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b73ae95dc148/bzImage-26285807.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+31c428...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 UID: 0 PID: 11530 Comm: syz.0.1024 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:const_folio_flags include/linux/page-flags.h:351 [inline]
RIP: 0010:folio_test_locked include/linux/page-flags.h:551 [inline]
RIP: 0010:__readahead_folio include/linux/pagemap.h:1418 [inline]
RIP: 0010:readahead_folio include/linux/pagemap.h:1434 [inline]
RIP: 0010:mpage_readahead+0x1bf/0x790 fs/mpage.c:367
Code: 89 e7 e8 b4 27 dc ff 49 8b 3c 24 48 83 c7 08 4c 89 fe e8 e4 2e 34 09 49 89 c7 48 8d 58 08 48 89 d8 48 c1 e8 03 48 89 44 24 38 <42> 80 3c 28 00 74 08 48 89 df e8 82 27 dc ff 4c 8b 33 4c 89 f6 48
RSP: 0000:ffffc900033e7180 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000008 RCX: 51d85eb9eea76500
RDX: 0000000000000001 RSI: ffffffff8dd8dcaa RDI: ffff888033155ac0
RBP: ffffc900033e7370 R08: ffff888033155ac0 R09: 0000000000000002
R10: 0000000000000406 R11: 0000000000000002 R12: ffffc900033e7728
R13: dffffc0000000000 R14: 0000000000000010 R15: 0000000000000000
FS: 00007fcda82b16c0(0000) GS:ffff8881259fc000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3331bff8 CR3: 000000007529a000 CR4: 00000000003526f0
Call Trace:
<TASK>
read_pages+0x17a/0x580 mm/readahead.c:163
page_cache_ra_unbounded+0x75e/0x9a0 mm/readahead.c:302
filemap_get_pages+0x468/0x1de0 mm/filemap.c:2638
filemap_splice_read+0x581/0xc60 mm/filemap.c:3027
do_splice_read fs/splice.c:982 [inline]
splice_direct_to_actor+0x4a9/0xcc0 fs/splice.c:1086
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0x181/0x270 fs/splice.c:1230
do_sendfile+0x4da/0x7e0 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1417
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcda738eec9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcda82b1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fcda75e5fa0 RCX: 00007fcda738eec9
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000004
RBP: 00007fcda7411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020fffe82 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcda75e6038 R14: 00007fcda75e5fa0 R15: 00007ffdad18ac88
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:const_folio_flags include/linux/page-flags.h:351 [inline]
RIP: 0010:folio_test_locked include/linux/page-flags.h:551 [inline]
RIP: 0010:__readahead_folio include/linux/pagemap.h:1418 [inline]
RIP: 0010:readahead_folio include/linux/pagemap.h:1434 [inline]
RIP: 0010:mpage_readahead+0x1bf/0x790 fs/mpage.c:367
Code: 89 e7 e8 b4 27 dc ff 49 8b 3c 24 48 83 c7 08 4c 89 fe e8 e4 2e 34 09 49 89 c7 48 8d 58 08 48 89 d8 48 c1 e8 03 48 89 44 24 38 <42> 80 3c 28 00 74 08 48 89 df e8 82 27 dc ff 4c 8b 33 4c 89 f6 48
RSP: 0000:ffffc900033e7180 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000008 RCX: 51d85eb9eea76500
RDX: 0000000000000001 RSI: ffffffff8dd8dcaa RDI: ffff888033155ac0
RBP: ffffc900033e7370 R08: ffff888033155ac0 R09: 0000000000000002
R10: 0000000000000406 R11: 0000000000000002 R12: ffffc900033e7728
R13: dffffc0000000000 R14: 0000000000000010 R15: 0000000000000000
FS: 00007fcda82b16c0(0000) GS:ffff8881259fc000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555657bd608 CR3: 000000007529a000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 89 e7 mov %esp,%edi
2: e8 b4 27 dc ff call 0xffdc27bb
7: 49 8b 3c 24 mov (%r12),%rdi
b: 48 83 c7 08 add $0x8,%rdi
f: 4c 89 fe mov %r15,%rsi
12: e8 e4 2e 34 09 call 0x9342efb
17: 49 89 c7 mov %rax,%r15
1a: 48 8d 58 08 lea 0x8(%rax),%rbx
1e: 48 89 d8 mov %rbx,%rax
21: 48 c1 e8 03 shr $0x3,%rax
25: 48 89 44 24 38 mov %rax,0x38(%rsp)
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 df mov %rbx,%rdi
34: e8 82 27 dc ff call 0xffdc27bb
39: 4c 8b 33 mov (%rbx),%r14
3c: 4c 89 f6 mov %r14,%rsi
3f: 48 rex.W


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup