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Message-Id: <20250712161813.44b62c947535cb78a3a4c9be@linux-foundation.org> Date: Sat, 12 Jul 2025 16:18:13 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: 白烁冉 <baishuoran@...eu.edu.cn> Cc: "Kun Hu" <huk23@...udan.edu.cn>, "Jiaji Qin" <jjtan24@...udan.edu.cn>, syzkaller@...glegroups.com, linux-kernel@...r.kernel.org, ocfs2-devel@...ts.linux.dev Subject: Re: BUG: unable to handle kernel paging request in const_folio_flags (cc ocfs2-devel) On Fri, 11 Jul 2025 17:58:46 +0800 (GMT+08:00) 白烁冉 <baishuoran@...eu.edu.cn> wrote: > Dear Maintainers, > > > When using our customized Syzkaller to fuzz the latest Linux kernel, the following crash (121th)was triggered. > > > > > HEAD commit: 6537cfb395f352782918d8ee7b7f10ba2cc3cbf2 > git tree: upstream > Output: https://github.com/pghk13/Kernel-Bug/blob/main/0702_6.14/BUG%3A%20unable%20to%20handle%20kernel%20paging%20request%20in%20const_folio_flags/121report.txt > Kernel config:https://github.com/pghk13/Kernel-Bug/blob/main/0702_6.14/config.txt > C reproducer:https://github.com/pghk13/Kernel-Bug/blob/main/0702_6.14/BUG%3A%20unable%20to%20handle%20kernel%20paging%20request%20in%20const_folio_flags/121repro.c > Syzlang reproducer:https://github.com/pghk13/Kernel-Bug/blob/main/0702_6.14/BUG%3A%20unable%20to%20handle%20kernel%20paging%20request%20in%20const_folio_flags/121repro.txt > > Our reproducer uses mounts a constructed filesystem image. > > This may be an error code mistakenly used as a pointer bug, occurring around line 308 of the code: 1. OCFS2 error handling issue: ocfs2_write_begin_nolock returns -ENOMEM (-12) when it encounters a memory allocation failure. 2. Incorrect error handling: In the error handling path, a certain function (most likely ocfs2_unlock_and_free_folios) incorrectly passed the error code -12 as a valid folio pointer to folio_unlock. > > We have reproduced this issue several times on 6.14 again. > > > > > > > If you fix this issue, please add the following tag to the commit: > Reported-by: Kun Hu <huk23@...udan.edu.cn>, Jiaji Qin <jjtan24@...udan.edu.cn>, Shuoran Bai <baishuoran@...eu.edu.cn> > > (syz.5.1560,31124,2):ocfs2_write_begin_nolock:1798 ERROR: status = -12 > BUG: unable to handle page fault for address: fffffffffffffffc > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD df84067 P4D df84067 PUD df86067 > PMD 0 > Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI > CPU: 2 UID: 0 PID: 31124 Comm: syz.5.1560 Not tainted 6.14.0 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > RIP: 0010:const_folio_flags.constprop.0+0x27/0x70 > Code: 90 90 90 41 54 49 89 fc 53 e8 65 c3 ca ff 49 8d 7c 24 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 3e <49> 8b 5c 24 08 31 ff 83 e3 01 48 89 de e8 77 c5 ca ff 48 85 db 75 > RSP: 0018:ffffc90011eef678 EFLAGS: 00010246 > RAX: dffffc0000000000 RBX: ffff888079f54030 RCX: ffffffff839c06f7 > RDX: 1fffffffffffffff RSI: ffff888059b2a480 RDI: fffffffffffffffc > RBP: fffffffffffffff4 R08: 0000000000000000 R09: fffffbfff20c2fa3 > R10: fffffbfff20c2fa2 R11: ffffffff90617d17 R12: fffffffffffffff4 > R13: 000000000000000e R14: dffffc0000000000 R15: 0000000000000001 > FS: 00007f2d805f6700(0000) GS:ffff88802b900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: fffffffffffffffc CR3: 000000004039e000 CR4: 0000000000750ef0 > PKRU: 80000000 > Call Trace: > <TASK> > folio_unlock+0x16/0xd0 > ocfs2_unlock_and_free_folios+0x8c/0x1b0 > ocfs2_write_begin_nolock+0x115d/0x4f60 > ocfs2_write_begin+0x1d9/0x350 > generic_perform_write+0x3e0/0x8c0 > __generic_file_write_iter+0x1f6/0x240 > ocfs2_file_write_iter+0xc44/0x2380 > vfs_write+0xba2/0x1100 > ksys_write+0x122/0x240 > do_syscall_64+0xcf/0x250 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f2d827acadd > Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 b0 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f2d805f5ba8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 00007f2d829a5fa0 RCX: 00007f2d827acadd > RDX: 000000000000045c RSI: 0000000020000400 RDI: 0000000000000005 > RBP: 00007f2d805f5c00 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004 > R13: 00007f2d829a5fac R14: 00007f2d829a6038 R15: 00007f2d805f5d40 > </TASK> > Modules linked in: > CR2: fffffffffffffffc > ---[ end trace 0000000000000000 ]--- > RIP: 0010:const_folio_flags.constprop.0+0x27/0x70 > Code: 90 90 90 41 54 49 89 fc 53 e8 65 c3 ca ff 49 8d 7c 24 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 3e <49> 8b 5c 24 08 31 ff 83 e3 01 48 89 de e8 77 c5 ca ff 48 85 db 75 > RSP: 0018:ffffc90011eef678 EFLAGS: 00010246 > RAX: dffffc0000000000 RBX: ffff888079f54030 RCX: ffffffff839c06f7 > RDX: 1fffffffffffffff RSI: ffff888059b2a480 RDI: fffffffffffffffc > RBP: fffffffffffffff4 R08: 0000000000000000 R09: fffffbfff20c2fa3 > R10: fffffbfff20c2fa2 R11: ffffffff90617d17 R12: fffffffffffffff4 > R13: 000000000000000e R14: dffffc0000000000 R15: 0000000000000001 > FS: 00007f2d805f6700(0000) GS:ffff88802b900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: fffffffffffffffc CR3: 000000004039e000 CR4: 0000000000750ef0 > PKRU: 80000000 > ---------------- > Code disassembly (best guess): > 0: 90 nop > 1: 90 nop > 2: 90 nop > 3: 41 54 push %r12 > 5: 49 89 fc mov %rdi,%r12 > 8: 53 push %rbx > 9: e8 65 c3 ca ff callq 0xffcac373 > e: 49 8d 7c 24 08 lea 0x8(%r12),%rdi > 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax > 1a: fc ff df > 1d: 48 89 fa mov %rdi,%rdx > 20: 48 c1 ea 03 shr $0x3,%rdx > 24: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) > 28: 75 3e jne 0x68 > * 2a: 49 8b 5c 24 08 mov 0x8(%r12),%rbx <-- trapping instruction > 2f: 31 ff xor %edi,%edi > 31: 83 e3 01 and $0x1,%ebx > 34: 48 89 de mov %rbx,%rsi > 37: e8 77 c5 ca ff callq 0xffcac5b3 > 3c: 48 85 db test %rbx,%rbx > 3f: 75 .byte 0x75 > > > > thanks, > Kun Hu
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