WARNING in v9fs_fid_get_acl (2)

Status: upstream: reported C repro on 2026/09/19 05:07
Subsystems: mm
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+de6fd6789748a8aa64a0@syzkaller.appspotmail.com
First crash: 4d23h, last: 4d18h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
bcb88973 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ✅ WARNING in v9fs_fid_get_acl (2) 2026/09/16 00:45 2026/09/16 00:45 2026/09/16 01:22 2daa4bb5
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] 9p: bound the xattr size used to allocate the ACL buffer 3 (3) 2026/09/19 13:29
[syzbot] [mm?] WARNING in v9fs_fid_get_acl (2) 1 (2) 2026/09/19 10:14
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in v9fs_fid_get_acl mm -1 syz, C error error 5678 345d 1388d 0/29 auto-obsoleted due to no activity on 2026/01/02 05:48
linux-6.6 WARNING in v9fs_fid_get_acl origin:upstream missing-backport -1 syz, C done 56 11d 459d 0/2 upstream: reported C repro on 2025/06/17 12:37

Sample crash report:
------------[ cut here ]------------
1
WARNING: mm/page_alloc.c:5340 at alloc_order_allowed mm/page_alloc.c:5340 [inline], CPU#0: syz.1.357/7872
WARNING: mm/page_alloc.c:5340 at __alloc_frozen_pages_noprof+0x2137/0x3300 mm/page_alloc.c:5397, CPU#0: syz.1.357/7872
Modules linked in:
CPU: 0 UID: 0 PID: 7872 Comm: syz.1.357 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:alloc_order_allowed mm/page_alloc.c:5340 [inline]
RIP: 0010:__alloc_frozen_pages_noprof+0x2137/0x3300 mm/page_alloc.c:5397
Code: 13 00 00 39 84 24 98 00 00 00 0f 85 4a fa ff ff e9 91 f6 ff ff 80 3d e2 93 bb 0e 00 0f 85 9d e2 ff ff c6 05 d5 93 bb 0e 01 90 <0f> 0b 90 e9 8d e2 ff ff 31 c0 e9 5f ec ff ff 48 8b 7c 24 08 48 c7
RSP: 0018:ffffc90004df7758 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000029 RDI: 0000000000040d40
RBP: 0000000000000029 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000029 R11: 0000000000000000 R12: 0000000000040d40
R13: 1ffff920009bef47 R14: 0000000000000000 R15: 1ffff920009bef05
FS:  00007fc8804026c0(0000) GS:ffff8880d5b59000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc88037dff8 CR3: 0000000037685000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 alloc_pages_mpol+0x201/0x550 mm/mempolicy.c:2486
 ___kmalloc_large_node+0xe8/0x130 mm/slub.c:5353
 __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:5385
 __do_kmalloc_node mm/slub.c:5402 [inline]
 __kmalloc_noprof+0x5a8/0x840 mm/slub.c:5439
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 v9fs_fid_get_acl+0x7a/0x120 fs/9p/acl.c:33
 __v9fs_get_acl fs/9p/acl.c:67 [inline]
 v9fs_get_acl+0xe8/0x480 fs/9p/acl.c:93
 v9fs_qid_iget_dotl fs/9p/vfs_inode_dotl.c:131 [inline]
 v9fs_inode_from_fid_dotl+0x26d/0x300 fs/9p/vfs_inode_dotl.c:154
 v9fs_get_new_inode_from_fid fs/9p/v9fs.h:264 [inline]
 v9fs_get_tree+0x55c/0xb50 fs/9p/vfs_super.c:120
 vfs_get_tree+0x92/0x320 fs/super.c:1933
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3772 [inline]
 do_new_mount fs/namespace.c:3848 [inline]
 path_mount+0x7d0/0x24c0 fs/namespace.c:4168
 do_mount fs/namespace.c:4181 [inline]
 __do_sys_mount fs/namespace.c:4397 [inline]
 __se_sys_mount fs/namespace.c:4374 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:4374
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc87f59e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc880402028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fc87f825fa0 RCX: 00007fc87f59e159
RDX: 0000200000000240 RSI: 0000200000000200 RDI: 0000000000000000
RBP: 00007fc87f63503b R08: 0000200000000180 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc87f826038 R14: 00007fc87f825fa0 R15: 00007ffeeb3b2c38
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/15 10:28 upstream 587858367581 81a27d1a .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in v9fs_fid_get_acl
2026/09/15 08:14 upstream 587858367581 81a27d1a .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in v9fs_fid_get_acl
2026/09/15 06:53 upstream 587858367581 81a27d1a .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in v9fs_fid_get_acl
2026/09/15 04:59 upstream 587858367581 81a27d1a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in v9fs_fid_get_acl
* Struck through repros no longer work on HEAD.