linux-kernel - Re: [syzbot] [fs?] [mm?] kernel BUG in __filemap_add

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Message-ID: <692c67e7.a70a0220.d98e3.0172.GAE@google.com>
Date: Sun, 30 Nov 2025 07:51:03 -0800
From: syzbot <syzbot+4d3cc33ef7a77041efa6@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, brauner@...nel.org, hare@...e.de, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, mcgrof@...nel.org, ssranevjti@...il.com, 
	syzkaller-bugs@...glegroups.com, willy@...radead.org
Subject: Re: [syzbot] [fs?] [mm?] kernel BUG in __filemap_add_folio

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in mpage_readahead

------------[ cut here ]------------
kernel BUG at ./include/linux/pagemap.h:1408!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 18176 Comm: syz-executor317 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__readahead_folio include/linux/pagemap.h:1408 [inline]
RIP: 0010:readahead_folio include/linux/pagemap.h:1434 [inline]
RIP: 0010:mpage_readahead+0x4ad/0x5a0 fs/mpage.c:367
Code: 5e 41 5f c3 cc cc cc cc e8 b0 19 70 ff 48 89 ef e8 48 06 ad ff e9 54 fe ff ff 4c 8b 6c 24 18 e9 43 ff ff ff e8 94 19 70 ff 90 <0f> 0b e8 8c 19 70 ff 48 c7 c6 00 b6 80 8b 48 89 ef e8 1d 39 ba ff
RSP: 0018:ffffc9000d92f620 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffc9000d92fae8 RCX: ffffffff824c7d14
RDX: ffff88802fe68000 RSI: ffffffff824c809c RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000004 R09: 0000000000000004
R10: 0000000000000001 R11: 0000000000000000 R12: dffffc0000000000
R13: fffff52001b25f61 R14: 0000000000000001 R15: 1ffff92001b25f61
FS:  0000555564bcd380(0000) GS:ffff888124f53000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f08297b0130 CR3: 0000000030a16000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 read_pages+0x1c4/0xc70 mm/readahead.c:163
 page_cache_ra_unbounded+0x66a/0xa10 mm/readahead.c:269
 do_page_cache_ra mm/readahead.c:332 [inline]
 page_cache_ra_order+0xc0b/0xf20 mm/readahead.c:542
 do_sync_mmap_readahead mm/filemap.c:3340 [inline]
 filemap_fault+0x1583/0x29a0 mm/filemap.c:3489
 __do_fault+0x10d/0x490 mm/memory.c:5281
 do_shared_fault mm/memory.c:5780 [inline]
 do_fault mm/memory.c:5854 [inline]
 do_pte_missing+0x1a6/0x3ba0 mm/memory.c:4362
 handle_pte_fault mm/memory.c:6195 [inline]
 __handle_mm_fault+0x1556/0x2aa0 mm/memory.c:6336
 handle_mm_fault+0x589/0xd10 mm/memory.c:6505
 do_user_addr_fault+0x60c/0x1370 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x64/0xc0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x7f082970586d
Code: 03 00 b9 03 10 12 00 45 31 c0 48 ba 80 00 00 00 00 20 00 00 48 b8 2f 64 65 76 2f 6e 75 6c 48 c7 c6 9c ff ff ff bf 01 01 00 00 <48> 89 02 48 b8 88 00 00 00 00 20 00 00 c7 00 6c 62 30 00 31 c0 e8
RSP: 002b:00007ffff735c180 EFLAGS: 00010246
RAX: 6c756e2f7665642f RBX: 0000000000000000 RCX: 0000000000121003
RDX: 0000200000000080 RSI: ffffffffffffff9c RDI: 0000000000000101
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000002000
R10: 0000000000000013 R11: 0000000000000206 R12: 0000000000079470
R13: 00007ffff735c19c R14: 00007ffff735c1b0 R15: 00007ffff735c1a0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__readahead_folio include/linux/pagemap.h:1408 [inline]
RIP: 0010:readahead_folio include/linux/pagemap.h:1434 [inline]
RIP: 0010:mpage_readahead+0x4ad/0x5a0 fs/mpage.c:367
Code: 5e 41 5f c3 cc cc cc cc e8 b0 19 70 ff 48 89 ef e8 48 06 ad ff e9 54 fe ff ff 4c 8b 6c 24 18 e9 43 ff ff ff e8 94 19 70 ff 90 <0f> 0b e8 8c 19 70 ff 48 c7 c6 00 b6 80 8b 48 89 ef e8 1d 39 ba ff
RSP: 0018:ffffc9000d92f620 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffc9000d92fae8 RCX: ffffffff824c7d14
RDX: ffff88802fe68000 RSI: ffffffff824c809c RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000004 R09: 0000000000000004
R10: 0000000000000001 R11: 0000000000000000 R12: dffffc0000000000
R13: fffff52001b25f61 R14: 0000000000000001 R15: 1ffff92001b25f61
FS:  0000555564bcd380(0000) GS:ffff888124f53000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f08297b0130 CR3: 0000000030a16000 CR4: 00000000003526f0


Tested on:

commit:         6bda50f4 Merge tag 'mips-fixes_6.18_2' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11857514580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f4a1ecf59be91960
dashboard link: https://syzkaller.appspot.com/bug?extid=4d3cc33ef7a77041efa6
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10dc7cb4580000