KASAN: use-after-free Read in rc_dev_uevent

Status: upstream: reported C repro on 2026/08/04 19:34
Reported-by: syzbot+23b1d1906b47c04d9a6d@syzkaller.appspotmail.com
First crash: 7d03h, last: 3d00h
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in rc_dev_uevent 19 syz, C 12 1d15h 6d20h 0/3 upstream: reported C repro on 2026/08/05 01:50
upstream KASAN: use-after-free Read in rc_dev_uevent media 19 1 2195d 2195d 15/29 fixed on 2020/09/25 01:17
upstream KASAN: slab-use-after-free Read in rc_dev_uevent media prio:high 19 syz, C 51 1d05h 6d00h 0/29 upstream: reported C repro on 2026/08/05 22:44
linux-6.6 KASAN: slab-use-after-free Read in rc_dev_uevent 19 syz, C 13 2d12h 7d01h 0/2 upstream: reported C repro on 2026/08/04 21:24

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:642 [inline]
BUG: KASAN: use-after-free in string+0x204/0x290 lib/vsprintf.c:724
Read of size 1 at addr ffff88807bd8e728 by task udevd/3560

CPU: 0 PID: 3560 Comm: udevd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 string_nocheck lib/vsprintf.c:642 [inline]
 string+0x204/0x290 lib/vsprintf.c:724
 vsnprintf+0x10db/0x1c20 lib/vsprintf.c:2811
 add_uevent_var+0x1cd/0x460 lib/kobject_uevent.c:680
 rc_dev_uevent+0x15b/0x190 drivers/media/rc/rc-main.c:1630
 dev_uevent+0x4d6/0x740 drivers/base/core.c:2361
 uevent_show+0x1b1/0x320 drivers/base/core.c:2410
 dev_attr_show+0x50/0xb0 drivers/base/core.c:2110
 sysfs_kf_seq_show+0x316/0x4c0 fs/sysfs/file.c:61
 seq_read_iter+0x460/0xc50 fs/seq_file.c:230
 call_read_iter include/linux/fs.h:2167 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x75e/0xd50 fs/read_write.c:485
 ksys_read+0x153/0x260 fs/read_write.c:623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f1e1c134407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffc8a481520 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f1e1c046880 RCX: 00007f1e1c134407
RDX: 0000000000001000 RSI: 000055c67fc0d550 RDI: 000000000000000c
RBP: 00007f1e1c27cff0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a
R13: 00007f1e1c27cea0 R14: 0000000000000000 R15: 000055c67fc295d0
 </TASK>

Allocated by task 2240:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 redrat3_dev_probe+0x3ef/0x23c0 drivers/media/rc/redrat3.c:1025
 usb_probe_interface+0x5be/0xae0 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x276/0xc70 drivers/base/dd.c:595
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805
 __device_attach_driver+0x2b0/0x500 drivers/base/dd.c:927
 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429
 __device_attach+0x2a7/0x480 drivers/base/dd.c:999
 bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489
 device_add+0xbcf/0x1050 drivers/base/core.c:3427
 usb_set_configuration+0x19d5/0x2030 drivers/usb/core/message.c:2223
 usb_generic_driver_probe+0x89/0x150 drivers/usb/core/generic.c:238
 usb_probe_device+0x126/0x250 drivers/usb/core/driver.c:293
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x276/0xc70 drivers/base/dd.c:595
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805
 __device_attach_driver+0x2b0/0x500 drivers/base/dd.c:927
 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429
 __device_attach+0x2a7/0x480 drivers/base/dd.c:999
 bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489
 device_add+0xbcf/0x1050 drivers/base/core.c:3427
 usb_new_device+0x9f6/0x15d0 drivers/usb/core/hub.c:2632
 hub_port_connect drivers/usb/core/hub.c:5497 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
 port_event drivers/usb/core/hub.c:5799 [inline]
 hub_event+0x2b8d/0x5260 drivers/usb/core/hub.c:5881
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 2240:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 redrat3_delete drivers/media/rc/redrat3.c:466 [inline]
 redrat3_dev_probe+0x1b69/0x23c0 drivers/media/rc/redrat3.c:1126
 usb_probe_interface+0x5be/0xae0 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x276/0xc70 drivers/base/dd.c:595
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805
 __device_attach_driver+0x2b0/0x500 drivers/base/dd.c:927
 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429
 __device_attach+0x2a7/0x480 drivers/base/dd.c:999
 bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489
 device_add+0xbcf/0x1050 drivers/base/core.c:3427
 usb_set_configuration+0x19d5/0x2030 drivers/usb/core/message.c:2223
 usb_generic_driver_probe+0x89/0x150 drivers/usb/core/generic.c:238
 usb_probe_device+0x126/0x250 drivers/usb/core/driver.c:293
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x276/0xc70 drivers/base/dd.c:595
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805
 __device_attach_driver+0x2b0/0x500 drivers/base/dd.c:927
 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429
 __device_attach+0x2a7/0x480 drivers/base/dd.c:999
 bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489
 device_add+0xbcf/0x1050 drivers/base/core.c:3427
 usb_new_device+0x9f6/0x15d0 drivers/usb/core/hub.c:2632
 hub_port_connect drivers/usb/core/hub.c:5497 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
 port_event drivers/usb/core/hub.c:5799 [inline]
 hub_event+0x2b8d/0x5260 drivers/usb/core/hub.c:5881
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff88807bd8e000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1832 bytes inside of
 2048-byte region [ffff88807bd8e000, ffff88807bd8e800)
The buggy address belongs to the page:
page:ffffea0001ef6200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7bd88
head:ffffea0001ef6200 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888016c42000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4313, ts 86970740383, free_ts 86742177508
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x807/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 __kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 __alloc_skb+0x22c/0x750 net/core/skbuff.c:427
 alloc_skb include/linux/skbuff.h:1162 [inline]
 mld_newpack+0x12f/0xba0 net/ipv6/mcast.c:1773
 add_grhead net/ipv6/mcast.c:1884 [inline]
 add_grec+0x1364/0x1840 net/ipv6/mcast.c:2023
 mld_send_cr net/ipv6/mcast.c:2146 [inline]
 mld_ifc_work+0x6f2/0xd60 net/ipv6/mcast.c:2690
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
 free_slab mm/slub.c:2020 [inline]
 discard_slab mm/slub.c:2026 [inline]
 __unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
 put_cpu_partial+0x12d/0x190 mm/slub.c:2592
 qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc+0x189/0x340 mm/slub.c:4408
 kmalloc include/linux/slab.h:612 [inline]
 tomoyo_realpath_from_path+0xed/0x5e0 security/tomoyo/realpath.c:254
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_number_perm+0x251/0x6b0 security/tomoyo/file.c:723
 security_file_ioctl+0x6c/0xa0 security/security.c:1556
 __do_sys_ioctl fs/ioctl.c:868 [inline]
 __se_sys_ioctl+0x48/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff88807bd8e600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807bd8e680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807bd8e700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88807bd8e780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807bd8e800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/08 22:44 linux-5.15.y aabd761612db 5d63f80b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in rc_dev_uevent
2026/08/05 02:27 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in rc_dev_uevent
2026/08/05 02:25 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in rc_dev_uevent
2026/08/04 19:34 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in rc_dev_uevent
* Struck through repros no longer work on HEAD.