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

Status: upstream: reported on 2026/09/06 00:24
Subsystems: mmc
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+f312381a95cc080992fd@syzkaller.appspotmail.com
First crash: 49d, last: 1d02h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
7be26673 repro-c Reproduced: ✅ ❓ KASAN: slab-use-after-free Read in mmc_host_classdev_release 2026/09/07 14:10 2026/09/07 14:10 2026/09/07 15:56 680aa3e1
a8dc7c77 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in mmc_host_classdev_release 2026/09/06 00:00 2026/09/06 00:00 2026/09/06 00:23 4f7b22a0
c4cbeb8c assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in mmc_host_classdev_release 2026/09/03 00:00 2026/09/03 00:00 2026/09/03 00:21 9941e97d
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[PATCH v3 2/2] mmc: core: don't dereference parent when releasing host index 1 (1) 2026/09/09 10:58
[PATCH v2] mmc: vub300: fix use-after-free in vub300 teardown 2 (2) 2026/09/08 15:51
[PATCH] mmc: vub300: fix use-after-free in vub300 teardown 5 (5) 2026/09/08 15:08
[syzbot] [mmc?] KASAN: slab-use-after-free Read in mmc_host_classdev_release 0 (1) 2026/09/06 00:24
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/07 16:54 12m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git df2908090cda368b01ff43709f51890076c56157 report job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in mmc_host_classdev_release+0x7c/0x100 drivers/mmc/core/host.c:70
Read of size 8 at addr ffff88804e494580 by task kworker/u8:4/65

CPU: 0 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: kvub300d vub300_deadwork_thread
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
 mmc_host_classdev_release+0x7c/0x100 drivers/mmc/core/host.c:70
 device_release+0xc4/0x1f0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x222/0x550 lib/kobject.c:737
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 5792:
 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:409 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3d5/0x680 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 usb_alloc_dev+0x5f/0xf20 drivers/usb/core/usb.c:651
 hub_port_connect drivers/usb/core/hub.c:5488 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
 port_event drivers/usb/core/hub.c:5889 [inline]
 hub_event+0x2113/0x4cf0 drivers/usb/core/hub.c:5971
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 65:
 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:264 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6509 [inline]
 kfree+0x1c5/0x6d0 mm/slub.c:6802
 device_release+0xc4/0x1f0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x222/0x550 lib/kobject.c:737
 vub300_delete drivers/mmc/host/vub300.c:378 [inline]
 kref_put include/linux/kref.h:65 [inline]
 vub300_deadwork_thread+0x2ba/0x530 drivers/mmc/host/vub300.c:-1
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff88804e494000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1408 bytes inside of
 freed 4096-byte region [ffff88804e494000, ffff88804e495000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4e490
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ff04140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ff04140 dead000000000100 dead000000000122
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 00000007f6a3b621 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3352, tgid 3352 (kworker/u8:13), ts 145113228528
 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+0x2591/0x2600 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x230/0x5c0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab+0x7d/0x620 mm/slub.c:3462
 new_slab mm/slub.c:3513 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7418
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x339/0x690 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_node_track_caller_noprof+0x61e/0x7b0 mm/slub.c:5545
 kmalloc_reserve net/core/skbuff.c:637 [inline]
 __alloc_skb+0x2c1/0x7a0 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:744 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:801 [inline]
 nsim_dev_trap_report_work+0x2b1/0xcb0 drivers/net/netdevsim/dev.c:847
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 5599 tgid 5599 ts 144984425091 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xf8e/0x1070 mm/page_alloc.c:2962
 __slab_free+0x250/0x2a0 mm/slub.c:5823
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:361
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 kmem_cache_alloc_noprof+0x360/0x690 mm/slub.c:5010
 anon_vma_chain_alloc mm/rmap.c:142 [inline]
 anon_vma_clone+0x3f3/0x9f0 mm/rmap.c:346
 anon_vma_fork+0x177/0x540 mm/rmap.c:408
 dup_mmap+0x9ad/0x1d80 mm/mmap.c:1781
 dup_mm kernel/fork.c:1543 [inline]
 copy_mm+0x115/0x480 kernel/fork.c:1595
 copy_process+0x1ea8/0x4490 kernel/fork.c:2321
 kernel_clone+0x2d2/0x8d0 kernel/fork.c:2781
 __do_sys_clone kernel/fork.c:2923 [inline]
 __se_sys_clone kernel/fork.c:2907 [inline]
 __x64_sys_clone+0x1b6/0x230 kernel/fork.c:2907
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88804e494480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804e494500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804e494580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88804e494600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804e494680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/20 06:14 upstream c03c1a14507d 72cdc28d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in mmc_host_classdev_release
2026/09/19 18:20 upstream 40288c9206c1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in mmc_host_classdev_release
2026/10/04 05:32 upstream a74306e2e676 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: slab-use-after-free Read in mmc_host_classdev_release
2026/09/01 18:26 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 5704a4065c2c 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in mmc_host_classdev_release
* Struck through repros no longer work on HEAD.