[syzbot] [mm?] general protection fault in shmem_get_next_id

[syzbot]

Hello,

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@xxxxxxxxxxxxxxxxxxxxxxxxx

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


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