KASAN: use-after-free Read in __vma_adjust

Status: upstream: reported C repro on 2022/06/12 10:38
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+68771c0e74f7bb7804e5@syzkaller.appspotmail.com
Fix commit: fs/userfaultfd: fix vma iteration in mas_for_each() loop
Patched on: [ci-upstream-linux-next-kasan-gce-root], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 1516d, last: 1460d
Cause bisection: introduced by (bisect log) :
commit d3ccd17e7c9647b956d415acdf3e3fde7ae9e20c
Author: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Thu Jun 9 20:57:09 2022 +0000

  mm: start tracking VMAs with maple tree

Crash: KASAN: use-after-free Read in __vma_adjust (log)
Repro: C syz .config
  
▶ ▼ ✨ AI Jobs (6)
ID Workflow Result Correct Bug Created Started Finished Revision
622b5ca6 assessment-security 💥 KASAN: use-after-free Read in __vma_adjust 2026/07/09 01:28 2026/07/09 01:28 2026/07/09 01:47 93f57954
6662a062 assessment-security 💥 KASAN: use-after-free Read in __vma_adjust 2026/06/22 03:21 2026/06/22 03:21 2026/06/22 03:36 43bfcdb0
511c1259 assessment-security 💥 KASAN: use-after-free Read in __vma_adjust 2026/06/14 02:40 2026/06/14 02:40 2026/06/14 02:56 4f06757f
2ba7076c assessment-security 💥 KASAN: use-after-free Read in __vma_adjust 2026/06/09 18:32 2026/06/09 18:32 2026/06/09 18:51 c36c07f6
d3845542 assessment-security 💥 KASAN: use-after-free Read in __vma_adjust 2026/06/02 15:47 2026/06/02 15:47 2026/06/02 16:09 62fe1528
ba9c4492 assessment-security 💥 KASAN: use-after-free Read in __vma_adjust 2026/05/25 21:00 2026/05/25 21:00 2026/05/25 21:22 c69befb3
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] KASAN: use-after-free Read in __vma_adjust 1 (3) 2022/06/15 16:45
[PATCH] fs/userfaultfd: Fix vma iteration in mas_for_each() loop 1 (1) 2022/06/15 16:42
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2022/06/14 10:50 18m hdanton@sina.com patch https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 6d0c80680317 OK log
2022/06/13 10:47 9m hdanton@sina.com patch https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 6d0c80680317 report log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __vma_adjust+0x18ee/0x1900 mm/mmap.c:763
Read of size 8 at addr ffff88801fefe208 by task syz-executor408/3621

CPU: 0 PID: 3621 Comm: syz-executor408 Not tainted 5.19.0-rc1-next-20220610-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
 print_report mm/kasan/report.c:429 [inline]
 kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
 __vma_adjust+0x18ee/0x1900 mm/mmap.c:763
 vma_merge+0x590/0x870 mm/mmap.c:1119
 userfaultfd_release+0x4c5/0x670 fs/userfaultfd.c:888
 __fput+0x277/0x9d0 fs/file_table.c:317
 task_work_run+0xdd/0x1a0 kernel/task_work.c:177
 ptrace_notify+0x114/0x140 kernel/signal.c:2353
 ptrace_report_syscall include/linux/ptrace.h:420 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
 syscall_exit_work kernel/entry/common.c:249 [inline]
 syscall_exit_to_user_mode_prepare+0xdb/0x230 kernel/entry/common.c:276
 __syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
 syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f2d02e9ef59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 71 15 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2d02e502f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffe00 RBX: 00007f2d02f284a8 RCX: 00007f2d02e9ef59
RDX: 000000000000003c RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00007f2d02f284a0 R08: 0000000000000001 R09: 0000000000000034
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2d02e50300
R13: 0000000000000001 R14: 00007f2d02e50400 R15: 0000000000022000
 </TASK>

Allocated by task 3619:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:436 [inline]
 __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
 kasan_slab_alloc include/linux/kasan.h:224 [inline]
 slab_post_alloc_hook mm/slab.h:750 [inline]
 slab_alloc_node mm/slub.c:3214 [inline]
 slab_alloc mm/slub.c:3222 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
 kmem_cache_alloc+0x204/0x3b0 mm/slub.c:3239
 vm_area_dup+0x81/0x380 kernel/fork.c:466
 dup_mmap+0x656/0x1090 kernel/fork.c:640
 dup_mm+0x91/0x370 kernel/fork.c:1520
 copy_mm kernel/fork.c:1569 [inline]
 copy_process+0x3c95/0x7080 kernel/fork.c:2234
 kernel_clone+0xe7/0xab0 kernel/fork.c:2649
 __do_sys_clone+0xba/0x100 kernel/fork.c:2783
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Freed by task 3621:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track+0x21/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1727 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
 slab_free mm/slub.c:3507 [inline]
 kmem_cache_free+0xdd/0x5a0 mm/slub.c:3524
 __vma_adjust+0x9ab/0x1900 mm/mmap.c:886
 vma_merge+0x590/0x870 mm/mmap.c:1119
 userfaultfd_release+0x4c5/0x670 fs/userfaultfd.c:888
 __fput+0x277/0x9d0 fs/file_table.c:317
 task_work_run+0xdd/0x1a0 kernel/task_work.c:177
 ptrace_notify+0x114/0x140 kernel/signal.c:2353
 ptrace_report_syscall include/linux/ptrace.h:420 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
 syscall_exit_work kernel/entry/common.c:249 [inline]
 syscall_exit_to_user_mode_prepare+0xdb/0x230 kernel/entry/common.c:276
 __syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
 syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

The buggy address belongs to the object at ffff88801fefe1b0
 which belongs to the cache vm_area_struct of size 152
The buggy address is located 88 bytes inside of
 152-byte region [ffff88801fefe1b0, ffff88801fefe248)

The buggy address belongs to the physical page:
page:ffffea00007fbf80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1fefe
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea00009ed380 dead000000000003 ffff888140006b40
raw: 0000000000000000 0000000000120012 00000001ffffffff 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 3327, tgid 3327 (rm), ts 28524505479, free_ts 28520297867
 prep_new_page mm/page_alloc.c:2460 [inline]
 get_page_from_freelist+0xa64/0x3d10 mm/page_alloc.c:4279
 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5500
 alloc_pages+0x1aa/0x310 mm/mempolicy.c:2279
 alloc_slab_page mm/slub.c:1797 [inline]
 allocate_slab+0x26c/0x3c0 mm/slub.c:1942
 new_slab mm/slub.c:2002 [inline]
 ___slab_alloc+0x985/0xd90 mm/slub.c:3002
 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3089
 slab_alloc_node mm/slub.c:3180 [inline]
 slab_alloc mm/slub.c:3222 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
 kmem_cache_alloc+0x360/0x3b0 mm/slub.c:3239
 vm_area_dup+0x81/0x380 kernel/fork.c:466
 __split_vma+0x9f/0x530 mm/mmap.c:2273
 do_mas_align_munmap+0x2c0/0xf00 mm/mmap.c:2399
 do_mas_munmap+0x202/0x2c0 mm/mmap.c:2556
 mmap_region+0x219/0x1bf0 mm/mmap.c:2604
 do_mmap+0x825/0xf60 mm/mmap.c:1480
 vm_mmap_pgoff+0x1b7/0x290 mm/util.c:520
 ksys_mmap_pgoff+0x40d/0x5a0 mm/mmap.c:1526
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1375 [inline]
 free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1425
 free_unref_page_prepare mm/page_alloc.c:3311 [inline]
 free_unref_page_list+0x184/0x1530 mm/page_alloc.c:3475
 release_pages+0xff1/0x2290 mm/swap.c:980
 tlb_batch_pages_flush+0xa8/0x1a0 mm/mmu_gather.c:58
 tlb_flush_mmu_free mm/mmu_gather.c:255 [inline]
 tlb_flush_mmu mm/mmu_gather.c:262 [inline]
 tlb_finish_mmu+0x147/0x7e0 mm/mmu_gather.c:353
 exit_mmap+0x217/0x750 mm/mmap.c:3205
 __mmput+0x128/0x4c0 kernel/fork.c:1180
 mmput+0x5c/0x70 kernel/fork.c:1201
 exec_mmap fs/exec.c:1038 [inline]
 begin_new_exec+0xfbd/0x2e50 fs/exec.c:1297
 load_elf_binary+0x15a3/0x4ec0 fs/binfmt_elf.c:1002
 search_binary_handler fs/exec.c:1728 [inline]
 exec_binprm fs/exec.c:1769 [inline]
 bprm_execve fs/exec.c:1838 [inline]
 bprm_execve+0x7ef/0x1970 fs/exec.c:1800
 do_execveat_common+0x724/0x890 fs/exec.c:1943
 do_execve fs/exec.c:2017 [inline]
 __do_sys_execve fs/exec.c:2093 [inline]
 __se_sys_execve fs/exec.c:2088 [inline]
 __x64_sys_execve+0x8f/0xc0 fs/exec.c:2088
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Memory state around the buggy address:
 ffff88801fefe100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
 ffff88801fefe180: fc fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb
>ffff88801fefe200: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
                      ^
 ffff88801fefe280: fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88801fefe300: 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00
==================================================================

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2022/06/12 09:47 linux-next 6d0c80680317 0d5abf15 .config strace log report syz C ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/08/07 11:24 linux-next cb71b93c2dc3 88e3a122 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/08/06 07:09 linux-next cb71b93c2dc3 e853abd9 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/07/10 20:22 linux-next cb71b93c2dc3 b5765a15 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/07/09 10:24 linux-next cb71b93c2dc3 b5765a15 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/07/08 02:53 linux-next cb71b93c2dc3 bff65f44 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/07/03 04:07 linux-next cb71b93c2dc3 1434eec0 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/06/30 07:23 linux-next cb71b93c2dc3 1434eec0 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/06/26 09:47 linux-next 2f9cb3d3bd73 a371c43c .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
2022/06/12 09:26 linux-next 6d0c80680317 0d5abf15 .config console log report info ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in __vma_adjust
* Struck through repros no longer work on HEAD.