KASAN: slab-use-after-free Read in netfs_unbuffered

ID	Workflow	Result	Correct	Bug	Created	Started	Finished	Revision	Error
b2fe841c	assessment-security	DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌	❓	KASAN: slab-use-after-free Read in netfs_unbuffered_write	2026/05/29 22:56	2026/05/29 22:56	2026/05/29 23:33	6b4a8443

assessment-security

DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌

❓

KASAN: slab-use-after-free Read in netfs_unbuffered_write

2026/05/29 22:56

2026/05/29 23:33

6b4a8443

Title	Replies (including bot)	Last reply
[PATCH v3 15/15] netfs: Fix DIO write retry for filesystems without a ->prepare_write()	1 (1)	2026/06/25 14:06
[syzbot] [netfs?] KASAN: slab-use-after-free Read in netfs_unbuffered_write	4 (10)	2026/06/25 13:16
[PATCH v2 14/14] netfs: Fix DIO write retry for filesystems without a ->prepare_write()	2 (2)	2026/06/24 14:21
[PATCH] netfs: Fix UAF in netfs_unbuffered_write() on failed preparation	9 (9)	2026/06/24 11:02

Title

Replies (including bot)

Last reply

[PATCH v3 15/15] netfs: Fix DIO write retry for filesystems without a ->prepare_write()

1 (1)

2026/06/25 14:06

[syzbot] [netfs?] KASAN: slab-use-after-free Read in netfs_unbuffered_write

4 (10)

2026/06/25 13:16

[PATCH v2 14/14] netfs: Fix DIO write retry for filesystems without a ->prepare_write()

2 (2)

2026/06/24 14:21

[PATCH] netfs: Fix UAF in netfs_unbuffered_write() on failed preparation

9 (9)

2026/06/24 11:02

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	BUG: unable to handle kernel NULL pointer dereference in netfs_unbuffered_write netfs	19	C			494	78d	141d	29/29	fixed on 2026/05/21 07:50

Rank 🛈

upstream

BUG: unable to handle kernel NULL pointer dereference in netfs_unbuffered_write netfs

494

78d

141d

29/29

fixed on 2026/05/21 07:50


Created	Duration	User	Patch	Repo	Result
2026/06/25 12:51	24m	dhowells@redhat.com	patch	git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 8fde5d1d47f6	log
2026/06/24 11:04	25m	dhowells@redhat.com	patch	git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 8fde5d1d47f6	OK log
2026/06/19 22:22	18m	retest repro		upstream	report log
2026/06/19 22:22	19m	retest repro		upstream	report log
2026/05/31 04:37	23m	eadavis@qq.com	patch	upstream	log
2026/05/31 03:44	18m	eadavis@qq.com	patch	upstream	report log
2026/05/30 02:13	18m	hongao@uniontech.com	patch	upstream	report log

================================================================== BUG: KASAN: slab-use-after-free in netfs_unbuffered_write+0x1c21/0x21e0 fs/netfs/direct_write.c:119 Read of size 2 at addr ffff888022e87864 by task syz.0.17/5936 CPU: 1 UID: 0 PID: 5936 Comm: syz.0.17 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 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x13d/0x4b0 mm/kasan/report.c:482 kasan_report+0xdf/0x1d0 mm/kasan/report.c:595 netfs_unbuffered_write+0x1c21/0x21e0 fs/netfs/direct_write.c:119 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:294 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:386 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1070 fs/read_write.c:688 ksys_write+0x12a/0x250 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f2eecd9ce59 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:00007f2eedc49028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f2eed015fa0 RCX: 00007f2eecd9ce59 RDX: 00000000fffffdd8 RSI: 0000200000000540 RDI: 0000000000000003 RBP: 00007f2eece32d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f2eed016038 R14: 00007f2eed015fa0 R15: 00007fff0ed7a0b8 </TASK> Allocated by task 5936: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4570 [inline] slab_alloc_node mm/slub.c:4899 [inline] kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4906 mempool_alloc_noprof+0x1b7/0x310 mm/mempool.c:566 netfs_alloc_subrequest+0xc1/0x3c0 fs/netfs/objects.c:204 netfs_prepare_write+0x76/0x780 fs/netfs/write_issue.c:172 netfs_unbuffered_write+0x7b8/0x21e0 fs/netfs/direct_write.c:111 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:294 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:386 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1070 fs/read_write.c:688 ksys_write+0x12a/0x250 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5936: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2689 [inline] slab_free mm/slub.c:6251 [inline] kmem_cache_free+0x127/0x6c0 mm/slub.c:6378 mempool_free+0xde/0x130 mm/mempool.c:711 netfs_free_subrequest fs/netfs/objects.c:239 [inline] netfs_put_subrequest+0x282/0x4c0 fs/netfs/objects.c:255 netfs_unbuffered_write+0x13ed/0x21e0 fs/netfs/direct_write.c:118 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:294 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:386 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1070 fs/read_write.c:688 ksys_write+0x12a/0x250 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff888022e877c0 which belongs to the cache netfs_subrequest of size 200 The buggy address is located 164 bytes inside of freed 200-byte region [ffff888022e877c0, ffff888022e87888) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x22e86 head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 memcg:ffff888026b62001 flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000040 ffff88801fab5680 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800190019 00000000f5000000 ffff888026b62001 head: 00fff00000000040 ffff88801fab5680 dead000000000100 dead000000000122 head: 0000000000000000 0000000800190019 00000000f5000000 ffff888026b62001 head: 00fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 4032896346, free_ts 0 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853 prep_new_page mm/page_alloc.c:1861 [inline] get_page_from_freelist+0x11a6/0x3410 mm/page_alloc.c:3941 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5221 alloc_slab_page mm/slub.c:3278 [inline] allocate_slab mm/slub.c:3467 [inline] new_slab+0xa6/0x6c0 mm/slub.c:3525 refill_objects+0x277/0x420 mm/slub.c:7272 refill_sheaf mm/slub.c:2816 [inline] __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652 alloc_from_pcs mm/slub.c:4750 [inline] slab_alloc_node mm/slub.c:4884 [inline] kmem_cache_alloc_noprof+0x480/0x6e0 mm/slub.c:4906 mempool_init_node+0x2f7/0x6e0 mm/mempool.c:259 mempool_init_noprof+0x3a/0x50 mm/mempool.c:289 netfs_init+0x16c/0x2b0 fs/netfs/main.c:128 do_one_initcall+0x121/0x750 init/main.c:1392 do_initcall_level init/main.c:1454 [inline] do_initcalls init/main.c:1470 [inline] do_basic_setup init/main.c:1490 [inline] kernel_init_freeable+0x6ea/0x7b0 init/main.c:1703 kernel_init+0x1f/0x1e0 init/main.c:1593 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 page_owner free stack trace missing Memory state around the buggy address: ffff888022e87700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888022e87780: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb >ffff888022e87800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888022e87880: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888022e87900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================

Crashes (8):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Assets (help?)	Manager	Title
2026/05/29 02:16	upstream	8fde5d1d47f6	4624854e	.config	console log	report	syz / log	C		[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/05/28 23:55	upstream	8fde5d1d47f6	4624854e	.config	console log	report	syz / log	C		[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/06/05 20:28	upstream	ddd664bbff63	48b6c3fa	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/06/02 03:39	upstream	e43ffb69e043	1095583b	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/05/28 23:29	upstream	8fde5d1d47f6	4624854e	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/05/28 23:29	upstream	8fde5d1d47f6	4624854e	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/06/30 07:57	upstream	dc59e4fea9d8	fff8d0a0	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream-386	KASAN: slab-use-after-free Read in netfs_unbuffered_write
2026/06/26 12:34	upstream	4edcdefd4083	7ff32d8b	.config	console log	report			info	[disk image (non-bootable)] [vmlinux] [kernel image]	ci-qemu-upstream-386	KASAN: slab-use-after-free Read in netfs_unbuffered_write

Crashes (8):

Assets (help?)