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: 19d, last: 1d19h
▶ ▼ ✨ 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+0xfb/0x120 drivers/mmc/core/host.c:70
Read of size 8 at addr ffff88802c08d4c8 by task kworker/u8:2/40

CPU: 0 UID: 0 PID: 40 Comm: kworker/u8:2 Tainted: G      
CPU: 0 UID: 0 PID: 40 Comm: kworker/u8:2 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Workqueue: kvub300d vub300_deadwork_thread
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/0x1c0 mm/kasan/report.c:595
 mmc_host_classdev_release+0xfb/0x120 drivers/mmc/core/host.c:70
 device_release+0xd2/0x270 drivers/base/core.c:2640
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3884
 vub300_delete drivers/mmc/host/vub300.c:379 [inline]
 kref_put include/linux/kref.h:65 [inline]
 vub300_deadwork_thread+0x22c/0x550 drivers/mmc/host/vub300.c:739
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 5762:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x2f8/0x6d0 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 usb_alloc_dev+0x55/0x1090 drivers/usb/core/usb.c:651
 hub_port_connect drivers/usb/core/hub.c:5483 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5720 [inline]
 port_event drivers/usb/core/hub.c:5884 [inline]
 hub_event+0x2b93/0x4420 drivers/usb/core/hub.c:5966
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 10:
 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:2748 [inline]
 slab_free mm/slub.c:6508 [inline]
 kfree+0x22b/0x6d0 mm/slub.c:6801
 device_release+0xd2/0x270 drivers/base/core.c:2640
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3884
 hub_port_connect drivers/usb/core/hub.c:5420 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5720 [inline]
 port_event drivers/usb/core/hub.c:5884 [inline]
 hub_event+0x1bb1/0x4420 drivers/usb/core/hub.c:5966
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 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 ffff88802c08d000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1224 bytes inside of
 freed 2048-byte region [ffff88802c08d000, ffff88802c08d800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2c088
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801c035000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801c035000 dead000000000100 dead000000000122
head: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 9059019829
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35d0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab mm/slub.c:3462 [inline]
 new_slab+0xa9/0x6e0 mm/slub.c:3513
 refill_objects+0xe3/0x410 mm/slub.c:7417
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __kmalloc_cache_noprof+0x4f4/0x6d0 mm/slub.c:5559
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 usb_hub_create_port_device+0x79/0xe60 drivers/usb/core/port.c:759
 hub_configure drivers/usb/core/hub.c:1739 [inline]
 hub_probe.cold+0x2974/0x2ed9 drivers/usb/core/hub.c:2006
 usb_probe_interface+0x386/0x9b0 drivers/usb/core/driver.c:399
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:706
 __driver_probe_device+0x210/0x460 drivers/base/dd.c:868
 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88802c08d380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802c08d400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802c08d480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff88802c08d500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802c08d580: 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
2026/09/19 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
2026/09/01 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.