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Date: Wed, 3 Apr 2024 18:33:39 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: syzbot <syzbot+05e63c0981a31f35f3fa@syzkaller.appspotmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
 syzkaller-bugs@googlegroups.com, Carlos Maiolino <cem@kernel.org>,
 Christian Brauner <brauner@kernel.org>
Subject: Re: [syzbot] [mm?] general protection fault in shmem_get_next_id
Message-Id: <20240403183339.7a257066e79ac04a7d6e33fd@linux-foundation.org>
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On Mon, 01 Apr 2024 23:58:20 -0700 syzbot <syzbot+05e63c0981a31f35f3fa@syzkaller.appspotmail.com> wrote:

> Hello,

Hello.

Seems that the new TMPFS_QUOTA code has blown up.  Cc's added, thanks
for the report and the reproducer!

> syzbot found the following issue on:
> 
> HEAD commit:    fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=10c90795180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=fe78468a74fdc3b7
> dashboard link: https://syzkaller.appspot.com/bug?extid=05e63c0981a31f35f3fa
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f51129180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=150d3cee180000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/0f7abe4afac7/disk-fe46a7dd.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/82598d09246c/vmlinux-fe46a7dd.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/efa23788c875/bzImage-fe46a7dd.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+05e63c0981a31f35f3fa@syzkaller.appspotmail.com
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 0 PID: 5070 Comm: syz-executor253 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> RIP: 0010:shmem_get_next_id+0x92/0x5c0 mm/shmem_quota.c:119
> Code: 04 db 49 8d 9c c6 90 02 00 00 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 f8 66 1b 00 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 df 66 1b 00 4c 8b 23 48 8d 5d 07
> RSP: 0018:ffffc900043a7be0 EFLAGS: 00010256
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8880266c8000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000004
> RBP: ffffc900043a7d00 R08: ffffffff81dcdd47 R09: ffffffff822e7d5a
> R10: 0000000000000003 R11: ffffffff81dcdcf0 R12: 1ffff92000874fa0
> R13: ffff888022110000 R14: ffff888022110000 R15: dffffc0000000000
> FS:  0000555578677380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020001000 CR3: 000000007a384000 CR4: 0000000000350ef0
> Call Trace:
>  <TASK>
>  dquot_get_next_dqblk+0x75/0x3a0 fs/quota/dquot.c:2705
>  quota_getnextquota+0x2c7/0x6c0 fs/quota/quota.c:250
>  __do_sys_quotactl_fd fs/quota/quota.c:1002 [inline]
>  __se_sys_quotactl_fd+0x2a1/0x440 fs/quota/quota.c:973
>  do_syscall_64+0xfd/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7f5c0349b329
> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc39d71138 EFLAGS: 00000246 ORIG_RAX: 00000000000001bb
> RAX: ffffffffffffffda RBX: 0031656c69662f2e RCX: 00007f5c0349b329
> RDX: 0000000000000000 RSI: ffffffff80000901 RDI: 0000000000000003
> RBP: 00007f5c0350e610 R08: 0000000000000000 R09: 00007ffc39d71308
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffc39d712f8 R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:shmem_get_next_id+0x92/0x5c0 mm/shmem_quota.c:119
> Code: 04 db 49 8d 9c c6 90 02 00 00 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 f8 66 1b 00 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 df 66 1b 00 4c 8b 23 48 8d 5d 07
> RSP: 0018:ffffc900043a7be0 EFLAGS: 00010256
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8880266c8000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000004
> RBP: ffffc900043a7d00 R08: ffffffff81dcdd47 R09: ffffffff822e7d5a
> R10: 0000000000000003 R11: ffffffff81dcdcf0 R12: 1ffff92000874fa0
> R13: ffff888022110000 R14: ffff888022110000 R15: dffffc0000000000
> FS:  0000555578677380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020001000 CR3: 000000007a384000 CR4: 0000000000350ef0
> ----------------
> Code disassembly (best guess):
>    0:	04 db                	add    $0xdb,%al
>    2:	49 8d 9c c6 90 02 00 	lea    0x290(%r14,%rax,8),%rbx
>    9:	00
>    a:	48 89 d8             	mov    %rbx,%rax
>    d:	48 c1 e8 03          	shr    $0x3,%rax
>   11:	42 80 3c 38 00       	cmpb   $0x0,(%rax,%r15,1)
>   16:	74 08                	je     0x20
>   18:	48 89 df             	mov    %rbx,%rdi
>   1b:	e8 f8 66 1b 00       	call   0x1b6718
>   20:	48 8b 1b             	mov    (%rbx),%rbx
>   23:	48 89 d8             	mov    %rbx,%rax
>   26:	48 c1 e8 03          	shr    $0x3,%rax
> * 2a:	42 80 3c 38 00       	cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
>   2f:	74 08                	je     0x39
>   31:	48 89 df             	mov    %rbx,%rdi
>   34:	e8 df 66 1b 00       	call   0x1b6718
>   39:	4c 8b 23             	mov    (%rbx),%r12
>   3c:	48 8d 5d 07          	lea    0x7(%rbp),%rbx
> 
> 
> ---
> 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 syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
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> 
> If the report is already addressed, let syzbot know by replying with:
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> 
> If you want syzbot to run the reproducer, reply with:
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> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
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> (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:
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