KASAN: slab-use-after-free Read in mas_next_slot (2)

Status: auto-obsoleted due to no activity on 2025/10/24 06:43
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+ebfd0e44b5c11034e1eb@syzkaller.appspotmail.com
First crash: 394d, last: 394d
Cause bisection: introduced by (bisect log) :
commit ef69a41567549aa8ba7deb350ab1f3f55011591d
Author: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Date: Fri Jul 11 11:38:23 2025 +0000

  mm/mremap: permit mremap() move of multiple VMAs

Crash: KASAN: slab-use-after-free Read in mas_next_slot (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] KASAN: slab-use-after-free Read in mas_next_slot (2) 10 (13) 2025/07/18 12:56
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in mas_next_slot mm 19 4 1137d 1135d 0/29 auto-obsoleted due to no activity on 2023/10/11 19:44
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2025/10/08 18:55 27m retest repro linux-next no crash log
2025/07/30 11:50 23m retest repro linux-next error
2025/07/17 01:46 22m hdanton@sina.com patch linux-next report log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in ma_dead_node lib/maple_tree.c:575 [inline]
BUG: KASAN: slab-use-after-free in mas_rewalk_if_dead lib/maple_tree.c:4415 [inline]
BUG: KASAN: slab-use-after-free in mas_next_slot+0x185/0xcf0 lib/maple_tree.c:4697
Read of size 8 at addr ffff8880755dc600 by task syz.0.656/6830

CPU: 1 UID: 0 PID: 6830 Comm: syz.0.656 Not tainted 6.16.0-rc6-next-20250714-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:378 [inline]
 print_report+0xca/0x230 mm/kasan/report.c:480
 kasan_report+0x118/0x150 mm/kasan/report.c:593
 ma_dead_node lib/maple_tree.c:575 [inline]
 mas_rewalk_if_dead lib/maple_tree.c:4415 [inline]
 mas_next_slot+0x185/0xcf0 lib/maple_tree.c:4697
 mas_find+0xb0e/0xd30 lib/maple_tree.c:6062
 vma_find include/linux/mm.h:855 [inline]
 remap_move mm/mremap.c:1819 [inline]
 do_mremap mm/mremap.c:1904 [inline]
 __do_sys_mremap mm/mremap.c:1968 [inline]
 __se_sys_mremap+0xaff/0xef0 mm/mremap.c:1936
 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: 0033:0x7f4fecf8e929
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:00007fff93ea4718 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f4fed1b5fa0 RCX: 00007f4fecf8e929
RDX: 0000000000600002 RSI: 0000000000600002 RDI: 0000200000000000
RBP: 00007f4fed010b39 R08: 0000200000a00000 R09: 0000000000000000
R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4fed1b5fa0 R14: 00007f4fed1b5fa0 R15: 0000000000000005
 </TASK>

Allocated by task 6830:
 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:4180 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4236
 mt_alloc_one lib/maple_tree.c:176 [inline]
 mas_alloc_nodes+0x2e9/0x8e0 lib/maple_tree.c:1255
 mas_node_count_gfp lib/maple_tree.c:1337 [inline]
 mas_preallocate+0x3ad/0x6f0 lib/maple_tree.c:5537
 vma_iter_prealloc mm/vma.h:463 [inline]
 __split_vma+0x2fa/0xa00 mm/vma.c:528
 vms_gather_munmap_vmas+0x2de/0x12b0 mm/vma.c:1359
 __mmap_prepare mm/vma.c:2361 [inline]
 __mmap_region mm/vma.c:2653 [inline]
 mmap_region+0x724/0x20c0 mm/vma.c:2741
 do_mmap+0xc45/0x10d0 mm/mmap.c:561
 vm_mmap_pgoff+0x2a6/0x4d0 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

Freed by task 23:
 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:2417 [inline]
 slab_free mm/slub.c:4680 [inline]
 kmem_cache_free+0x18f/0x400 mm/slub.c:4782
 rcu_do_batch kernel/rcu/tree.c:2584 [inline]
 rcu_core+0xca8/0x1710 kernel/rcu/tree.c:2840
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:968
 smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

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
 __call_rcu_common kernel/rcu/tree.c:3102 [inline]
 call_rcu+0x157/0x9c0 kernel/rcu/tree.c:3222
 mas_wr_node_store lib/maple_tree.c:3893 [inline]
 mas_wr_store_entry+0x1f1b/0x25b0 lib/maple_tree.c:4104
 mas_store_prealloc+0xb00/0xf60 lib/maple_tree.c:5510
 vma_iter_store_new mm/vma.h:509 [inline]
 vma_complete+0x224/0xae0 mm/vma.c:354
 __split_vma+0x8a6/0xa00 mm/vma.c:568
 vms_gather_munmap_vmas+0x2de/0x12b0 mm/vma.c:1359
 do_vmi_align_munmap+0x25d/0x420 mm/vma.c:1527
 do_vmi_munmap+0x253/0x2e0 mm/vma.c:1584
 do_munmap+0xe1/0x140 mm/mmap.c:1071
 mremap_to+0x304/0x7b0 mm/mremap.c:1367
 remap_move mm/mremap.c:1861 [inline]
 do_mremap mm/mremap.c:1904 [inline]
 __do_sys_mremap mm/mremap.c:1968 [inline]
 __se_sys_mremap+0xa0b/0xef0 mm/mremap.c:1936
 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 ffff8880755dc600
 which belongs to the cache maple_node of size 256
The buggy address is located 0 bytes inside of
 freed 256-byte region [ffff8880755dc600, ffff8880755dc700)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x755dc
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a491000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a491000 dead000000000122 0000000000000000
head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0001d57701 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6828, tgid 6828 (cmp), ts 120765032919, free_ts 112542256570
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2487 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2655
 new_slab mm/slub.c:2709 [inline]
 ___slab_alloc+0xbeb/0x1410 mm/slub.c:3891
 __slab_alloc mm/slub.c:3981 [inline]
 __slab_alloc_node mm/slub.c:4056 [inline]
 slab_alloc_node mm/slub.c:4217 [inline]
 kmem_cache_alloc_noprof+0x283/0x3c0 mm/slub.c:4236
 mt_alloc_one lib/maple_tree.c:176 [inline]
 mas_alloc_nodes+0x2e9/0x8e0 lib/maple_tree.c:1255
 mas_node_count_gfp lib/maple_tree.c:1337 [inline]
 mas_preallocate+0x3ad/0x6f0 lib/maple_tree.c:5537
 vma_iter_prealloc mm/vma.h:463 [inline]
 commit_merge+0x1fd/0x700 mm/vma.c:753
 vma_expand+0x40c/0x7e0 mm/vma.c:1158
 vma_merge_new_range+0x6a3/0x860 mm/vma.c:1095
 __mmap_region mm/vma.c:2666 [inline]
 mmap_region+0xd46/0x20c0 mm/vma.c:2741
 do_mmap+0xc45/0x10d0 mm/mmap.c:561
 vm_mmap_pgoff+0x2a6/0x4d0 mm/util.c:579
 ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607
page last free pid 5955 tgid 5955 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2895
 __slab_free+0x303/0x3c0 mm/slub.c:4591
 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:4180 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4236
 getname_flags+0xb8/0x540 fs/namei.c:146
 getname include/linux/fs.h:2914 [inline]
 do_sys_openat2+0xbc/0x1c0 fs/open.c:1429
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1461
 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:
 ffff8880755dc500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880755dc580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880755dc600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880755dc680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880755dc700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/16 06:42 linux-next 0be23810e32e 03fcfc4b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in mas_next_slot
2025/07/16 04:26 linux-next 0be23810e32e 03fcfc4b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in mas_next_slot
2025/07/16 03:19 linux-next 0be23810e32e 03fcfc4b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in mas_next_slot
* Struck through repros no longer work on HEAD.