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

From: syzbot
Date: Wed Jun 18 2025 - 08:56:46 EST

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Hello,

syzbot found the following issue on:

HEAD commit: bc6e0ba6c9ba Add linux-next specific files for 20250613
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=108c710c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2f7a2e4d17ed458f
dashboard link: https://syzkaller.appspot.com/bug?extid=8e4be574cb8c40140a2a
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=148c710c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=179025d4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2430bb0465cc/disk-bc6e0ba6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/436a39deef0a/vmlinux-bc6e0ba6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e314ca5b1eb3/bzImage-bc6e0ba6.xz

The issue was bisected to:

commit 3b61a3f08949297815b2c77ae2696f54cd339419
Author: Ryan Roberts <ryan.roberts@xxxxxxx>
Date: Mon Jun 9 09:27:27 2025 +0000

mm/filemap: allow arch to request folio size for exec memory

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11b0a5d4580000
final oops: https://syzkaller.appspot.com/x/report.txt?x=13b0a5d4580000
console output: https://syzkaller.appspot.com/x/log.txt?x=15b0a5d4580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8e4be574cb8c40140a2a@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 3b61a3f08949 ("mm/filemap: allow arch to request folio size for exec memory")

==================================================================
BUG: KASAN: slab-use-after-free in do_sync_mmap_readahead+0x4bf/0x830 mm/filemap.c:3282
Read of size 8 at addr ffff88806bda3410 by task syz-executor164/6247

CPU: 0 UID: 0 PID: 6247 Comm: syz-executor164 Not tainted 6.16.0-rc1-next-20250613-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0xd2/0x2b0 mm/kasan/report.c:521
kasan_report+0x118/0x150 mm/kasan/report.c:634
do_sync_mmap_readahead+0x4bf/0x830 mm/filemap.c:3282
filemap_fault+0x62c/0x1200 mm/filemap.c:3444
__do_fault+0x135/0x390 mm/memory.c:5187
do_read_fault mm/memory.c:5608 [inline]
do_fault mm/memory.c:5742 [inline]
do_pte_missing mm/memory.c:4269 [inline]
handle_pte_fault mm/memory.c:6087 [inline]
__handle_mm_fault+0x37ed/0x5620 mm/memory.c:6230
handle_mm_fault+0x40a/0x8e0 mm/memory.c:6399
faultin_page mm/gup.c:1186 [inline]
__get_user_pages+0x1aef/0x30b0 mm/gup.c:1488
populate_vma_page_range+0x29f/0x3a0 mm/gup.c:1922
__mm_populate+0x24c/0x380 mm/gup.c:2025
mm_populate include/linux/mm.h:3354 [inline]
vm_mmap_pgoff+0x3f0/0x4c0 mm/util.c:584
ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f580d0c3919
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f580d07c208 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f580d14d348 RCX: 00007f580d0c3919
RDX: 0000000001000006 RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f580d14d340 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000028011 R11: 0000000000000246 R12: 00007f580d11a270
R13: 00002000000001d8 R14: 00002000000005c0 R15: 00002000000001c0
</TASK>

Allocated by task 6247:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]
kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4204
vm_area_alloc+0x24/0x140 mm/vma_init.c:31
__mmap_new_vma mm/vma.c:2452 [inline]
__mmap_region mm/vma.c:2662 [inline]
mmap_region+0xe0d/0x2080 mm/vma.c:2732
do_mmap+0xc45/0x10d0 mm/mmap.c:561
vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579
ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6249:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2381 [inline]
slab_free_after_rcu_debug+0x129/0x2a0 mm/slub.c:4693
rcu_do_batch kernel/rcu/tree.c:2582 [inline]
rcu_core+0xca8/0x1710 kernel/rcu/tree.c:2838
handle_softirqs+0x283/0x870 kernel/softirq.c:579
__do_softirq kernel/softirq.c:613 [inline]
invoke_softirq kernel/softirq.c:453 [inline]
__irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
slab_free_hook mm/slub.c:2342 [inline]
slab_free mm/slub.c:4643 [inline]
kmem_cache_free+0x2f6/0x400 mm/slub.c:4745
remove_vma mm/vma.c:465 [inline]
vms_complete_munmap_vmas+0x626/0x8a0 mm/vma.c:1288
__mmap_complete mm/vma.c:2518 [inline]
__mmap_region mm/vma.c:2670 [inline]
mmap_region+0x1221/0x2080 mm/vma.c:2732
do_mmap+0xc45/0x10d0 mm/mmap.c:561
vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88806bda33c0
which belongs to the cache vm_area_struct of size 256
The buggy address is located 80 bytes inside of
freed 256-byte region [ffff88806bda33c0, ffff88806bda34c0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6bda3
ksm flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88814040ab40 ffffea0001b656c0 0000000000000003
raw: 0000000000000000 00000000000c000c 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5532, tgid 5532 (rm), ts 56329480650, free_ts 52472185128
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
alloc_slab_page mm/slub.c:2451 [inline]
allocate_slab+0x8a/0x3b0 mm/slub.c:2619
new_slab mm/slub.c:2673 [inline]
___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
__slab_alloc mm/slub.c:3949 [inline]
__slab_alloc_node mm/slub.c:4024 [inline]
slab_alloc_node mm/slub.c:4185 [inline]
kmem_cache_alloc_noprof+0x283/0x3c0 mm/slub.c:4204
vm_area_dup+0x2b/0x680 mm/vma_init.c:122
__split_vma+0x1a9/0xa00 mm/vma.c:512
vms_gather_munmap_vmas+0x2de/0x12b0 mm/vma.c:1354
__mmap_prepare mm/vma.c:2351 [inline]
__mmap_region mm/vma.c:2641 [inline]
mmap_region+0x71a/0x2080 mm/vma.c:2732
do_mmap+0xc45/0x10d0 mm/mmap.c:561
vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579
ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5212 tgid 5212 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1248 [inline]
__free_frozen_pages+0xc71/0xe70 mm/page_alloc.c:2706
__slab_free+0x326/0x400 mm/slub.c:4554
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x224/0x4f0 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]
tomoyo_realpath_from_path+0xe3/0x5d0 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x213/0x4b0 security/tomoyo/file.c:822
security_inode_getattr+0x12f/0x330 security/security.c:2377
vfs_getattr fs/stat.c:259 [inline]
vfs_statx_path fs/stat.c:299 [inline]
vfs_statx+0x18e/0x550 fs/stat.c:356
vfs_fstatat+0x118/0x170 fs/stat.c:375
__do_sys_newfstatat fs/stat.c:542 [inline]
__se_sys_newfstatat fs/stat.c:536 [inline]
__x64_sys_newfstatat+0x116/0x190 fs/stat.c:536
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff88806bda3300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806bda3380: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff88806bda3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806bda3480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff88806bda3500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: Ulf Hansson: "Re: [PATCH] imx8m-blk-ctrl: set ISI panic write hurry level"
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