================================================================== ================================================================== BUG: KASAN: use-after-free in handle_userfault+0x1364/0x1550 fs/userfaultfd.c:407 Read of size 8 at addr ffff888023732190 by task syz-executor.4/14705 CPU: 0 PID: 14705 Comm: syz-executor.4 Not tainted 5.18.0-rc6-next-20220512-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __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 handle_userfault+0x1364/0x1550 fs/userfaultfd.c:407 shmem_getpage_gfp+0x1ab6/0x1f30 mm/shmem.c:1859 shmem_fault+0x1ae/0x750 mm/shmem.c:2078 __do_fault+0x107/0x650 mm/memory.c:4172 do_read_fault mm/memory.c:4518 [inline] do_fault mm/memory.c:4647 [inline] handle_pte_fault mm/memory.c:4910 [inline] __handle_mm_fault+0x2757/0x40f0 mm/memory.c:5049 handle_mm_fault+0x1c8/0x790 mm/memory.c:5147 do_user_addr_fault+0x489/0x11c0 arch/x86/mm/fault.c:1397 handle_page_fault arch/x86/mm/fault.c:1484 [inline] exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1540 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:570 RIP: 0033:0x7fc2df227c93 Code: 00 00 00 00 00 66 90 48 89 7c 24 f0 48 89 74 24 e8 48 89 54 24 e0 48 89 4c 24 d8 48 8b 4c 24 f0 48 8b 74 24 e8 4c 8b 44 24 e0 <8b> 81 0c 01 00 00 44 8b 89 08 01 00 00 48 8b 54 24 d8 c1 e0 04 8d RSP: 002b:00007fc2e03cb158 EFLAGS: 00010216 RAX: 00007fc2df227c70 RBX: 00007fc2df39bf60 RCX: 0000000020816000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020816000 RBP: 00007fc2df2e308d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020816000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007ffedc3ff0bf R14: 00007fc2e03cb300 R15: 0000000000022000 Allocated by task 14705: 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+0x142/0x3b0 mm/slub.c:3239 __do_sys_userfaultfd+0x9b/0x3e0 fs/userfaultfd.c:2098 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 14702: 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 userfaultfd_ctx_put fs/userfaultfd.c:180 [inline] userfaultfd_ctx_put+0x312/0x400 fs/userfaultfd.c:168 userfaultfd_release+0x399/0x670 fs/userfaultfd.c:917 __fput+0x277/0x9d0 fs/file_table.c:317 task_work_run+0xdd/0x1a0 kernel/task_work.c:177 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:169 [inline] exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:201 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline] syscall_exit_to_user_mode+0x19/0x50 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 ffff888023732000 which belongs to the cache userfaultfd_ctx_cache of size 408 The buggy address is located 400 bytes inside of 408-byte region [ffff888023732000, ffff888023732198) The buggy address belongs to the physical page: page:ffffea00008dcc80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x23732 head:ffffea00008dcc80 order:1 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 0000000000000000 dead000000000122 ffff88814798f3c0 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 1, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 14705, tgid 14702 (syz-executor.4), ts 678604763487, free_ts 656553503831 prep_new_page mm/page_alloc.c:2431 [inline] get_page_from_freelist+0x129e/0x3dd0 mm/page_alloc.c:4176 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5396 alloc_pages+0x1aa/0x310 mm/mempolicy.c:2280 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 __do_sys_userfaultfd+0x9b/0x3e0 fs/userfaultfd.c:2098 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 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1346 [inline] free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1396 free_unref_page_prepare mm/page_alloc.c:3318 [inline] free_unref_page+0x19/0x6a0 mm/page_alloc.c:3413 __unfreeze_partials+0x17c/0x1a0 mm/slub.c:2521 qlink_free mm/kasan/quarantine.c:168 [inline] qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187 kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:294 __kasan_slab_alloc+0xa2/0xc0 mm/kasan/common.c:446 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 getname_flags.part.0+0x50/0x4f0 fs/namei.c:139 getname_flags+0x9a/0xe0 include/linux/audit.h:323 vfs_fstatat+0x73/0xb0 fs/stat.c:254 __do_sys_newfstatat+0x91/0x110 fs/stat.c:425 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: ffff888023732080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888023732100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888023732180: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff888023732200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888023732280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================