[syzbot] [mm?] KASAN: slab-use-after-free Read in mtree_range_walk

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dcb6fa37fd7b Linux 6.18-rc3
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next
console output: https://syzkaller.appspot.com/x/log.txt?x=10da7012580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3106dc390828a333
dashboard link: https://syzkaller.appspot.com/bug?extid=131f9eb2b5807573275c
compiler: Debian clang version 20.1.8 (++20250708123704+0de59a293f7a-1~exp1~20250708003721.134), Debian LLD 20.1.8
userspace arch: arm64

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/fa3fbcfdac58/non_bootable_disk-dcb6fa37.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4a05d908f307/vmlinux-dcb6fa37.xz
kernel image: https://storage.googleapis.com/syzbot-assets/874b2b8dba2a/Image-dcb6fa37.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+131f9e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in ma_data_end lib/maple_tree.c:1255 [inline]
BUG: KASAN: slab-use-after-free in mtree_range_walk+0x604/0x8d0 lib/maple_tree.c:2556
Read of size 8 at addr 4cf000000dcf0178 by task syz.0.1606/8933
Pointer tag: [4c], memory tag: [fe]

CPU: 0 UID: 0 PID: 8933 Comm: syz.0.1606 Not tainted syzkaller #0 PREEMPT
Hardware name: linux,dummy-virt (DT)
Call trace:
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
__dump_stack+0x30/0x40 lib/dump_stack.c:94
dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
print_address_description+0xac/0x288 mm/kasan/report.c:378
print_report+0x84/0xa0 mm/kasan/report.c:482
kasan_report+0xb0/0x110 mm/kasan/report.c:595
kasan_tag_mismatch+0x28/0x3c mm/kasan/sw_tags.c:176
__hwasan_tag_mismatch+0x30/0x60 arch/arm64/lib/kasan_sw_tags.S:55
ma_data_end lib/maple_tree.c:1255 [inline]
mtree_range_walk+0x604/0x8d0 lib/maple_tree.c:2556
mas_state_walk lib/maple_tree.c:3296 [inline]
mas_walk+0xf8/0x34c lib/maple_tree.c:4597
lock_vma_under_rcu+0x10c/0x35c mm/mmap_lock.c:232
do_page_fault+0x3a8/0x1508 arch/arm64/mm/fault.c:625
do_translation_fault+0xbc/0xfc arch/arm64/mm/fault.c:789
do_mem_abort+0x50/0x110 arch/arm64/mm/fault.c:929
el0_da+0x64/0x210 arch/arm64/kernel/entry-common.c:562
el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:768
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Allocated by task 8934:
kasan_save_stack+0x40/0x6c mm/kasan/common.c:56
save_stack_info+0x30/0x138 mm/kasan/tags.c:106
kasan_save_alloc_info+0x14/0x20 mm/kasan/tags.c:142
unpoison_slab_object mm/kasan/common.c:342 [inline]
__kasan_slab_alloc+0x94/0x98 mm/kasan/common.c:368
kasan_slab_alloc include/linux/kasan.h:252 [inline]
slab_post_alloc_hook mm/slub.c:4970 [inline]
slab_alloc_node mm/slub.c:5280 [inline]
kmem_cache_alloc_noprof+0x320/0x5a8 mm/slub.c:5287
mt_alloc_one lib/maple_tree.c:172 [inline]
mas_alloc_nodes+0x350/0x3b8 lib/maple_tree.c:1108
mas_preallocate+0x544/0x970 lib/maple_tree.c:5192
vma_iter_prealloc mm/vma.h:442 [inline]
__split_vma+0x318/0xb00 mm/vma.c:528
vms_gather_munmap_vmas+0x4d0/0x1474 mm/vma.c:1380
__mmap_prepare mm/vma.c:2359 [inline]
__mmap_region mm/vma.c:2652 [inline]
mmap_region+0x6c0/0x1fcc mm/vma.c:2740
do_mmap+0xa50/0xf64 mm/mmap.c:558
vm_mmap_pgoff+0x290/0x3e8 mm/util.c:581
ksys_mmap_pgoff+0x3a4/0x448 mm/mmap.c:604
__do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
__se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
__arm64_sys_mmap+0x13c/0x198 arch/arm64/kernel/sys.c:21
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x90/0x238 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x180/0x2f4 arch/arm64/kernel/syscall.c:132
do_el0_svc+0x58/0x74 arch/arm64/kernel/syscall.c:151
el0_svc+0x5c/0x234 arch/arm64/kernel/entry-common.c:746
el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:765
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Freed by task 8110:
kasan_save_stack+0x40/0x6c mm/kasan/common.c:56
save_stack_info+0x30/0x138 mm/kasan/tags.c:106
__kasan_save_free_info+0x18/0x24 mm/kasan/tags.c:147
kasan_save_free_info mm/kasan/kasan.h:406 [inline]
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x64/0x68 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2539 [inline]
__rcu_free_sheaf_prepare+0x11c/0x2c4 mm/slub.c:2745
rcu_free_sheaf+0x2c/0x138 mm/slub.c:6181
rcu_do_batch kernel/rcu/tree.c:2605 [inline]
rcu_core+0xe14/0x1d30 kernel/rcu/tree.c:2861
rcu_core_si+0x10/0x1c kernel/rcu/tree.c:2878
handle_softirqs+0x36c/0xd08 kernel/softirq.c:622
__do_softirq+0x14/0x20 kernel/softirq.c:656

The buggy address belongs to the object at fff000000dcf0100
which belongs to the cache maple_node of size 256
The buggy address is located 120 bytes inside of
256-byte region [fff000000dcf0100, fff000000dcf0200)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xbbf000000dcf0000 pfn:0x4dcf0
flags: 0x1ffc00000000200(workingset|node=0|zone=0|lastcpupid=0x7ff|kasantag=0x0)
page_type: f5(slab)
raw: 01ffc00000000200 d5f000000cc09700 ffffc1ffc0494790 ffffc1ffc051fb90
raw: bbf000000dcf0000 000000000010000e 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
fff000000dceff00: ae ae ae ae ae ae ae ae ae ae ae ae ae ae ae ae
fff000000dcf0000: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
>fff000000dcf0100: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
^
fff000000dcf0200: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
fff000000dcf0300: 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70
==================================================================


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