[syzbot] [afs?] KASAN: slab-use-after-free Read in idr_get_free

From: syzbot
Date: Tue Apr 15 2025 - 06:25:02 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 29e7bf01ed80 Add linux-next specific files for 20250410
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13090f4c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a554d15459e77547
dashboard link: https://syzkaller.appspot.com/bug?extid=9197b322744974667353
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bb76302efd6b/disk-29e7bf01.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7da3c6b9e532/vmlinux-29e7bf01.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4909c61270ed/bzImage-29e7bf01.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9197b322744974667353@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-use-after-free in set_iter_tags lib/radix-tree.c:1123 [inline]
BUG: KASAN: slab-use-after-free in idr_get_free+0x959/0xac0 lib/radix-tree.c:1543
Read of size 8 at addr ffff888148c9cfe8 by task syz.2.19/5993

CPU: 0 UID: 0 PID: 5993 Comm: syz.2.19 Not tainted 6.15.0-rc1-next-20250410-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0x16e/0x5b0 mm/kasan/report.c:521
kasan_report+0x143/0x180 mm/kasan/report.c:634
set_iter_tags lib/radix-tree.c:1123 [inline]
idr_get_free+0x959/0xac0 lib/radix-tree.c:1543
idr_alloc_u32+0x197/0x330 lib/idr.c:46
idr_alloc_cyclic+0x108/0x310 lib/idr.c:125
afs_alloc_cell fs/afs/cell.c:202 [inline]
afs_lookup_cell+0xfad/0x18b0 fs/afs/cell.c:264
afs_parse_source fs/afs/super.c:292 [inline]
afs_parse_param+0x6f4/0x970 fs/afs/super.c:330
vfs_parse_fs_param+0x1a5/0x420 fs/fs_context.c:146
vfs_parse_fs_string+0x170/0x230 fs/fs_context.c:188
do_new_mount+0x26c/0xb70 fs/namespace.c:3873
do_mount fs/namespace.c:4219 [inline]
__do_sys_mount fs/namespace.c:4430 [inline]
__se_sys_mount+0x38c/0x400 fs/namespace.c:4407
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff4a198d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff4a2759038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ff4a1ba6240 RCX: 00007ff4a198d169
RDX: 00002000000000c0 RSI: 0000200000000080 RDI: 0000200000000040
RBP: 00007ff4a1a0e990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff4a1ba6240 R15: 00007ffda7d56bf8
</TASK>

Allocated by task 5997:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4151 [inline]
slab_alloc_node mm/slub.c:4200 [inline]
kmem_cache_alloc_noprof+0x1e1/0x390 mm/slub.c:4207
radix_tree_node_alloc+0x8b/0x3c0 lib/radix-tree.c:276
idr_get_free+0x296/0xac0 lib/radix-tree.c:1506
idr_alloc_u32+0x197/0x330 lib/idr.c:46
idr_alloc_cyclic+0x108/0x310 lib/idr.c:125
afs_alloc_cell fs/afs/cell.c:202 [inline]
afs_lookup_cell+0xfad/0x18b0 fs/afs/cell.c:264
afs_parse_source fs/afs/super.c:292 [inline]
afs_parse_param+0x6f4/0x970 fs/afs/super.c:330
vfs_parse_fs_param+0x1a5/0x420 fs/fs_context.c:146
vfs_parse_fs_string+0x170/0x230 fs/fs_context.c:188
do_new_mount+0x26c/0xb70 fs/namespace.c:3873
do_mount fs/namespace.c:4219 [inline]
__do_sys_mount fs/namespace.c:4430 [inline]
__se_sys_mount+0x38c/0x400 fs/namespace.c:4407
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6003:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2389 [inline]
slab_free mm/slub.c:4646 [inline]
kmem_cache_free+0x197/0x410 mm/slub.c:4748
rcu_do_batch kernel/rcu/tree.c:2568 [inline]
rcu_core+0xaac/0x17a0 kernel/rcu/tree.c:2824
handle_softirqs+0x2d6/0x9b0 kernel/softirq.c:579
__do_softirq kernel/softirq.c:613 [inline]
invoke_softirq kernel/softirq.c:453 [inline]
__irq_exit_rcu+0xfb/0x220 kernel/softirq.c:680
irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1049
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
kasan_record_aux_stack+0xbf/0xd0 mm/kasan/generic.c:548
__call_rcu_common kernel/rcu/tree.c:3082 [inline]
call_rcu+0x172/0xad0 kernel/rcu/tree.c:3202
radix_tree_node_free lib/radix-tree.c:310 [inline]
delete_node+0x1b2/0x780 lib/radix-tree.c:573
radix_tree_delete_item+0x2e6/0x3f0 lib/radix-tree.c:1430
afs_cell_destroy+0x175/0x2c0 fs/afs/cell.c:522
rcu_do_batch kernel/rcu/tree.c:2568 [inline]
rcu_core+0xaac/0x17a0 kernel/rcu/tree.c:2824
handle_softirqs+0x2d6/0x9b0 kernel/softirq.c:579
run_ksoftirqd+0xcf/0x130 kernel/softirq.c:968
smpboot_thread_fn+0x576/0xaa0 kernel/smpboot.c:164
kthread+0x7b7/0x940 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888148c9cdc0
which belongs to the cache radix_tree_node of size 576
The buggy address is located 552 bytes inside of
freed 576-byte region [ffff888148c9cdc0, ffff888148c9d000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x148c9c
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88814d1de401
ksm flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff88801b04bdc0 ffffea0005231f00 dead000000000003
raw: 0000000000000000 0000000000170017 00000000f5000000 ffff88814d1de401
head: 057ff00000000040 ffff88801b04bdc0 ffffea0005231f00 dead000000000003
head: 0000000000000000 0000000000170017 00000000f5000000 ffff88814d1de401
head: 057ff00000000002 ffffea0005232701 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Reclaimable, gfp_mask 0x52830(GFP_ATOMIC|__GFP_RECLAIMABLE|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 8730373092, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1718
prep_new_page mm/page_alloc.c:1726 [inline]
get_page_from_freelist+0x349b/0x3630 mm/page_alloc.c:3703
__alloc_frozen_pages_noprof+0x211/0x5b0 mm/page_alloc.c:4985
alloc_pages_mpol+0x339/0x690 mm/mempolicy.c:2301
alloc_slab_page mm/slub.c:2459 [inline]
allocate_slab+0x8f/0x3a0 mm/slub.c:2623
new_slab mm/slub.c:2676 [inline]
___slab_alloc+0xc3b/0x1500 mm/slub.c:3862
__slab_alloc+0x58/0xa0 mm/slub.c:3952
__slab_alloc_node mm/slub.c:4027 [inline]
slab_alloc_node mm/slub.c:4188 [inline]
kmem_cache_alloc_noprof+0x270/0x390 mm/slub.c:4207
radix_tree_node_alloc+0x19a/0x3c0 lib/radix-tree.c:253
idr_get_free+0x296/0xac0 lib/radix-tree.c:1506
idr_alloc_u32+0x197/0x330 lib/idr.c:46
idr_alloc_cyclic+0x108/0x310 lib/idr.c:125
__kernfs_new_node+0x12a/0x890 fs/kernfs/dir.c:643
kernfs_new_node+0x114/0x220 fs/kernfs/dir.c:713
kernfs_create_dir_ns+0x43/0x120 fs/kernfs/dir.c:1081
internal_create_group+0x528/0x1320 fs/sysfs/group.c:170
page_owner free stack trace missing

Memory state around the buggy address:
ffff888148c9ce80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888148c9cf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888148c9cf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888148c9d000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888148c9d080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
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Next message: Jan Kara: "Re: [PATCH v2] loop: properly send KOBJ_CHANGED uevent for disk device"
Previous message: Dhananjay Ugwekar: "[PATCH 1/2] cpufreq/amd-pstate: Add offline, online and suspend callbacks for amd_pstate_driver"
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