syzbot
KASAN: use-after-free Read in r1buf_pool_free
Status:
upstream: reported C repro on 2026/08/06 01:36
Reported-by: syzbot+281d1de0554287d3affb@syzkaller.appspotmail.com
First crash: 20d, last: 8d18h
Sample crash report:
md: md0: recovery done.
==================================================================
BUG: KASAN: use-after-free in r1buf_pool_free+0x130/0x134 drivers/md/raid1.c:228
Read of size 4 at addr ffff0000c3827c08 by task md0_resync/4533
CPU: 1 PID: 4533 Comm: md0_resync Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Call trace:
dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
print_address_description+0x88/0x218 mm/kasan/report.c:316
print_report+0x50/0x68 mm/kasan/report.c:420
kasan_report+0xa8/0xfc mm/kasan/report.c:524
__asan_report_load4_noabort+0x2c/0x38 mm/kasan/report_generic.c:350
r1buf_pool_free+0x130/0x134 drivers/md/raid1.c:228
mempool_exit+0x190/0x290 mm/mempool.c:174
close_sync drivers/md/raid1.c:1713 [inline]
raid1_sync_request+0x328/0x26e4 drivers/md/raid1.c:2696
md_do_sync+0x2e18/0x36ec drivers/md/md.c:9158
md_thread+0x1e0/0x3cc drivers/md/md.c:8000
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850
Allocated by task 4529:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:211 [inline]
kmalloc_trace+0x7c/0x94 mm/slab_common.c:1031
kmalloc include/linux/slab.h:563 [inline]
raid1_reshape+0x590/0x102c drivers/md/raid1.c:3289
chunk_size_store+0x1ec/0x358 drivers/md/md.c:4290
md_attr_store+0x168/0x234 drivers/md/md.c:5626
sysfs_kf_write+0x1f8/0x274 fs/sysfs/file.c:140
kernfs_fop_write_iter+0x390/0x4b4 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x3c8/0x7c8 fs/read_write.c:584
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Freed by task 4534:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
__kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
__kmem_cache_free+0xbc/0x21c mm/slub.c:3700
kfree+0xd0/0x1a8 mm/slab_common.c:988
raid1_reshape+0xc74/0x102c drivers/md/raid1.c:3332
chunk_size_store+0x1ec/0x358 drivers/md/md.c:4290
md_attr_store+0x168/0x234 drivers/md/md.c:5626
sysfs_kf_write+0x1f8/0x274 fs/sysfs/file.c:140
kernfs_fop_write_iter+0x390/0x4b4 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x3c8/0x7c8 fs/read_write.c:584
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Last potentially related work creation:
kasan_save_stack+0x40/0x70 mm/kasan/common.c:46
__kasan_record_aux_stack+0xc0/0xdc mm/kasan/generic.c:486
kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:496
kvfree_call_rcu+0xb4/0x6f0 kernel/rcu/tree.c:3405
kernfs_unlink_open_file+0x370/0x41c fs/kernfs/file.c:653
kernfs_fop_release+0x128/0x194 fs/kernfs/file.c:825
__fput+0x1b4/0x7b0 fs/file_table.c:320
____fput+0x20/0x30 fs/file_table.c:348
task_work_run+0x1f4/0x280 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
The buggy address belongs to the object at ffff0000c3827c00
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 8 bytes inside of
128-byte region [ffff0000c3827c00, ffff0000c3827c80)
The buggy address belongs to the physical page:
page:0000000024334aca refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x103827
flags: 0x5ffc00000000200(slab|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000200 fffffc0003103640 dead000000000004 ffff0000c0002300
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff0000c3827b00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff0000c3827b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000c3827c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff0000c3827c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff0000c3827d00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
==================================================================
Unable to handle kernel paging request at virtual address dfff800000000008
KASAN: null-ptr-deref in range [0x0000000000000040-0x0000000000000047]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff800000000008] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4533 Comm: md0_resync Tainted: G B syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 02400005 (nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : get_resync_pages drivers/md/raid1-10.c:90 [inline]
pc : r1buf_pool_free+0x90/0x134 drivers/md/raid1.c:229
lr : r1buf_pool_free+0x84/0x134 drivers/md/raid1.c:229
sp : ffff800021707500
x29: ffff800021707500 x28: 1fffe0001bedc44b x27: 1fffe0001bedc44e
x26: ffff80000ea38468 x25: 1fffe0001a43f080 x24: 00000000000011b5
x23: ffff0000d21ef658 x22: dfff800000000000 x21: 0000000000000040
x20: ffff0000d21f8400 x19: ffff0000d21ef600 x18: 1fffe00033e7697e
x17: 0000000000000000 x16: ffff800008043b30 x15: 0000000000000000
x14: 0000000000000001 x13: 1ffff00002ff016c x12: 0000000000000000
x11: ff0080000ea384c8 x10: 0000000000000000 x9 : ffff80001c5fab10
x8 : 0000000000000008 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800021706ed8 x4 : ffff800015464e80 x3 : ffff80000ea384ec
x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000000
Call trace:
get_resync_pages drivers/md/raid1-10.c:90 [inline]
r1buf_pool_free+0x90/0x134 drivers/md/raid1.c:229
mempool_exit+0x190/0x290 mm/mempool.c:174
close_sync drivers/md/raid1.c:1713 [inline]
raid1_sync_request+0x328/0x26e4 drivers/md/raid1.c:2696
md_do_sync+0x2e18/0x36ec drivers/md/md.c:9158
md_thread+0x1e0/0x3cc drivers/md/md.c:8000
kthread+0x254/0x2e0 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850
Code: 967af112 f9400288 91010115 d343fea8 (38766908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 967af112 bl 0xfffffffff9ebc448
4: f9400288 ldr x8, [x20]
8: 91010115 add x21, x8, #0x40
c: d343fea8 lsr x8, x21, #3
* 10: 38766908 ldrb w8, [x8, x22] <-- trapping instruction
Struck through repros no longer work on HEAD.