syzbot


KASAN: stack-out-of-bounds Write in fixup_umip_exception

Status: moderation: reported on 2025/01/20 12:52
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+4da6060bc1d743ea2779@syzkaller.appspotmail.com
First crash: 4d10h, last: 4d10h

Sample crash report:
loop0: detected capacity change from 0 to 4096
=======================================================
WARNING: The mand mount option has been deprecated and
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
ntfs3(loop0): Different NTFS sector size (1024) and media sector size (512).
ntfs3(loop0): Failed to load $Extend (-22).
ntfs3(loop0): Failed to initialize $Extend.
overlayfs: upper fs does not support tmpfile.
overlayfs: upper fs does not support RENAME_WHITEOUT.
==================================================================
BUG: KASAN: stack-out-of-bounds in fixup_umip_exception+0xe4/0x9f0 arch/x86/kernel/umip.c:344
Write of size 112 at addr ffffc9000d20fd20 by task syz.0.0/5314

CPU: 0 UID: 0 PID: 5314 Comm: syz.0.0 Not tainted 6.13.0-rc7-syzkaller-00043-g619f0b6fad52 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 __asan_memset+0x23/0x50 mm/kasan/shadow.c:84
 fixup_umip_exception+0xe4/0x9f0 arch/x86/kernel/umip.c:344
 __exc_general_protection arch/x86/kernel/traps.c:705 [inline]
 exc_general_protection+0x122/0x5d0 arch/x86/kernel/traps.c:693
 asm_exc_general_protection+0x26/0x30 arch/x86/include/asm/idtentry.h:617
WARNING: stack going in the wrong direction? at asm_exc_general_protection+0x26/0x30 arch/x86/include/asm/idtentry.h:617
 </TASK>

The buggy address belongs to stack of task syz.0.0/5314
 and is located at offset 160 in frame:
 fixup_umip_exception+0x0/0x9f0

This frame has 5 objects:
 [32, 40) 'dummy_base_addr.i'
 [64, 72) 'dummy_value.i'
 [96, 106) 'dummy_data'
 [128, 143) 'buf'
 [160, 272) 'insn'

The buggy address belongs to the virtual mapping at
 [ffffc9000d208000, ffffc9000d211000) created by:
 copy_process+0x5d1/0x3d50 kernel/fork.c:2224

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880408e1e00 pfn:0x408e1
memcg:ffff88804014f302
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: ffff8880408e1e00 0000000000000000 00000001ffffffff ffff88804014f302
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_ZERO), pid 30, tgid 30 (kworker/u4:2), ts 66517981617, free_ts 66517375821
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1558
 prep_new_page mm/page_alloc.c:1566 [inline]
 get_page_from_freelist+0x365c/0x37a0 mm/page_alloc.c:3476
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4753
 alloc_pages_mpol_noprof+0x3e1/0x780 mm/mempolicy.c:2269
 vm_area_alloc_pages mm/vmalloc.c:3591 [inline]
 __vmalloc_area_node mm/vmalloc.c:3669 [inline]
 __vmalloc_node_range_noprof+0x9c9/0x1380 mm/vmalloc.c:3846
 alloc_thread_stack_node kernel/fork.c:314 [inline]
 dup_task_struct+0x444/0x8c0 kernel/fork.c:1116
 copy_process+0x5d1/0x3d50 kernel/fork.c:2224
 kernel_clone+0x226/0x8e0 kernel/fork.c:2806
 user_mode_thread+0x132/0x1a0 kernel/fork.c:2884
 call_usermodehelper_exec_sync kernel/umh.c:132 [inline]
 call_usermodehelper_exec_work+0x9b/0x230 kernel/umh.c:163
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
 worker_thread+0x870/0xd30 kernel/workqueue.c:3398
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
page last free pid 5309 tgid 5309 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xe39/0x18b0 mm/page_alloc.c:2706
 folios_put_refs+0x76c/0x860 mm/swap.c:962
 free_pages_and_swap_cache+0x5c8/0x690 mm/swap_state.c:335
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:465
 exit_mmap+0x496/0xc20 mm/mmap.c:1685
 __mmput+0x115/0x3c0 kernel/fork.c:1348
 exit_mm+0x220/0x310 kernel/exit.c:570
 do_exit+0x9ad/0x28e0 kernel/exit.c:925
 do_group_exit+0x207/0x2c0 kernel/exit.c:1087
 __do_sys_exit_group kernel/exit.c:1098 [inline]
 __se_sys_exit_group kernel/exit.c:1096 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1096
 x64_sys_call+0x26a8/0x26b0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffffc9000d20fc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc9000d20fc80: f1 f1 f1 f1 00 f2 f2 f2 f3 f2 f2 f2 00 02 f2 f2
>ffffc9000d20fd00: 00 07 f2 f2 00 00 00 00 00 00 00 00 f1 f1 f1 f1
                                                       ^
 ffffc9000d20fd80: 00 00 f3 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00
 ffffc9000d20fe00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 f3
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/01/16 12:44 upstream 619f0b6fad52 968edaf4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: stack-out-of-bounds Write in fixup_umip_exception
* Struck through repros no longer work on HEAD.