KASAN: slab-use-after-free Read in fuse_dev_do_read (2)

Status: upstream: reported on 2026/07/24 00:52
Subsystems: fuse
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+25e06c2622d48c699eed@syzkaller.appspotmail.com
First crash: 52d, last: 52d
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
0bbdbb66 repro-c Reproduced: ✅ ❓ KASAN: slab-use-after-free Read in fuse_dev_do_read (2) 2026/08/16 13:31 2026/08/16 13:31 2026/08/16 16:22 746171ee
77530863 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in fuse_dev_do_read (2) 2026/07/24 00:24 2026/07/24 00:24 2026/07/24 00:51 71a13572
6db277bc assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in fuse_dev_do_read (2) 2026/07/21 00:44 2026/07/21 00:44 2026/07/21 01:35 de6a700d
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly fuse report (Aug 2026) 0 (1) 2026/08/02 04:32
[syzbot] [fuse?] KASAN: slab-use-after-free Read in fuse_dev_do_read (2) 0 (1) 2026/07/24 00:52
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in fuse_dev_do_read prio:high fuse 19 syz, C 2 129d 145d 0/29 closed as invalid on 2026/06/30 21:42
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/17 08:59 21m nogikh@google.com upstream no crash job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in fuse_dev_do_read+0x11e9/0x1260 fs/fuse/dev.c:1608
Read of size 1 at addr ffff88805f9b2818 by task syz.4.60/5955

CPU: 0 UID: 0 PID: 5955 Comm: syz.4.60 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 fuse_dev_do_read+0x11e9/0x1260 fs/fuse/dev.c:1608
 fuse_dev_read+0x16a/0x200 fs/fuse/dev.c:1694
 new_sync_read fs/read_write.c:493 [inline]
 vfs_read+0x59e/0xa90 fs/read_write.c:574
 ksys_read+0x156/0x270 fs/read_write.c:716
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f980f22e6ce
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007f980d4c5f68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f980d4c66c0 RCX: 00007f980f22e6ce
RDX: 0000000000002000 RSI: 0000200000004100 RDI: 0000000000000003
RBP: 00007f980f303eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 0000200000006d80 R14: 00007f980f4f5fa0 R15: 00007ffce2bcf0a8
 </TASK>

Allocated by task 5961:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3cd/0x670 mm/slub.c:5486
 _kmalloc_noprof include/linux/slab.h:969 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 fuse_new_init fs/fuse/inode.c:1445 [inline]
 fuse_send_init+0x58/0x820 fs/fuse/inode.c:1506
 vfs_get_super fs/super.c:1399 [inline]
 get_tree_nodev+0xbb/0x150 fs/super.c:1418
 fuse_get_tree+0x29d/0x3b0 fs/fuse/inode.c:1899
 vfs_get_tree+0x92/0x2a0 fs/super.c:1941
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3777 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3853
 do_mount fs/namespace.c:4186 [inline]
 __do_sys_mount fs/namespace.c:4402 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4379
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5961:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2706 [inline]
 slab_free mm/slub.c:6388 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6703
 process_init_reply+0x174/0x21b0 fs/fuse/inode.c:1424
 fuse_send_init+0x506/0x820 fs/fuse/inode.c:1521
 vfs_get_super fs/super.c:1399 [inline]
 get_tree_nodev+0xbb/0x150 fs/super.c:1418
 fuse_get_tree+0x29d/0x3b0 fs/fuse/inode.c:1899
 vfs_get_tree+0x92/0x2a0 fs/super.c:1941
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3777 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3853
 do_mount fs/namespace.c:4186 [inline]
 __do_sys_mount fs/namespace.c:4402 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4379
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88805f9b2800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
 freed 512-byte region [ffff88805f9b2800, ffff88805f9b2a00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88805f9b2400 pfn:0x5f9b0
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000240(workingset|head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000240 ffff88813feaec80 ffffea0000a7b710 ffffea0000a15f10
raw: ffff88805f9b2400 000000080010000d 00000000f5000000 0000000000000000
head: 0080000000000240 ffff88813feaec80 ffffea0000a7b710 ffffea0000a15f10
head: ffff88805f9b2400 000000080010000d 00000000f5000000 0000000000000000
head: 0080000000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5592, tgid 5592 (syz-executor), ts 88067380890
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x264c/0x26c0 mm/page_alloc.c:3955
 __alloc_frozen_pages_noprof+0x222/0x5b0 mm/page_alloc.c:5394
 alloc_slab_page mm/slub.c:3295 [inline]
 allocate_slab+0x7c/0x5e0 mm/slub.c:3410
 new_slab mm/slub.c:3456 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7321
 refill_sheaf mm/slub.c:2833 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4699
 alloc_from_pcs mm/slub.c:4775 [inline]
 slab_alloc_node mm/slub.c:4909 [inline]
 __do_kmalloc_node mm/slub.c:5338 [inline]
 __kmalloc_noprof+0x543/0x790 mm/slub.c:5364
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 fib6_info_alloc+0x30/0xf0 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x149/0x890 net/ipv6/route.c:3833
 addrconf_f6i_alloc+0x38b/0x630 net/ipv6/route.c:4702
 fixup_permanent_addr net/ipv6/addrconf.c:3611 [inline]
 addrconf_permanent_addr+0x4ab/0xa30 net/ipv6/addrconf.c:3662
 addrconf_notify+0x864/0x1050 net/ipv6/addrconf.c:3729
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2292 [inline]
 call_netdevice_notifiers net/core/dev.c:2306 [inline]
 __dev_notify_flags+0x31e/0x510 net/core/dev.c:9805
 netif_change_flags+0xde/0x1b0 net/core/dev.c:9834
 do_setlink+0xdd6/0x4670 net/core/rtnetlink.c:3246
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88805f9b2700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805f9b2780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805f9b2800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88805f9b2880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805f9b2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/19 21:01 linux-next cc2b5f627e8c 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in fuse_dev_do_read
2026/07/19 20:50 linux-next cc2b5f627e8c 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in fuse_dev_do_read
* Struck through repros no longer work on HEAD.