Hello, syzbot found the following issue on: HEAD commit: 1e1b28b936ae Add linux-next specific files for 20220513 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1441e8bef00000 kernel config: https://syzkaller.appspot.com/x/.config?x=e4eb3c0c4b289571 dashboard link: https://syzkaller.appspot.com/bug?extid=2972481db16665f2cb84 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 Unfortunately, I don't have any reproducer for this issue yet. IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+2972481db16665f2cb84@xxxxxxxxxxxxxxxxxxxxxxxxx ================================================================== ================================================================== BUG: KASAN: use-after-free in handle_userfault+0x1364/0x1550 fs/userfaultfd.c:407 Read of size 8 at addr ffff88807de28390 by task syz-executor.2/3998 CPU: 0 PID: 3998 Comm: syz-executor.2 Not tainted 5.18.0-rc6-next-20220513-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 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:4169 do_read_fault mm/memory.c:4515 [inline] do_fault mm/memory.c:4644 [inline] handle_pte_fault mm/memory.c:4907 [inline] __handle_mm_fault+0x2757/0x40f0 mm/memory.c:5046 handle_mm_fault+0x1c8/0x790 mm/memory.c:5144 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: 0033:0x7f2f83827c93 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:00007f2f84a73158 EFLAGS: 00010216 RAX: 00007f2f83827c70 RBX: 00007f2f8399bf60 RCX: 0000000020816000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020816000 RBP: 00007f2f838e308d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020816000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007ffe2fc20eaf R14: 00007f2f84a73300 R15: 0000000000022000 </TASK> Allocated by task 3998: 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 3998: 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 handle_userfault+0xfb6/0x1550 fs/userfaultfd.c:555 shmem_getpage_gfp+0x1ab6/0x1f30 mm/shmem.c:1859 shmem_fault+0x1ae/0x750 mm/shmem.c:2078 __do_fault+0x107/0x650 mm/memory.c:4169 do_read_fault mm/memory.c:4515 [inline] do_fault mm/memory.c:4644 [inline] handle_pte_fault mm/memory.c:4907 [inline] __handle_mm_fault+0x2757/0x40f0 mm/memory.c:5046 handle_mm_fault+0x1c8/0x790 mm/memory.c:5144 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 The buggy address belongs to the object at ffff88807de28200 which belongs to the cache userfaultfd_ctx_cache of size 408 The buggy address is located 400 bytes inside of 408-byte region [ffff88807de28200, ffff88807de28398) The buggy address belongs to the physical page: page:ffffea0001f78a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7de28 head:ffffea0001f78a00 order:1 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888145a11dc0 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 3955, tgid 3952 (syz-executor.2), ts 194794080949, free_ts 180867939487 prep_new_page mm/page_alloc.c:2439 [inline] get_page_from_freelist+0xa25/0x3d00 mm/page_alloc.c:4259 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5483 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:1354 [inline] free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1404 free_unref_page_prepare mm/page_alloc.c:3290 [inline] free_unref_page+0x19/0x7b0 mm/page_alloc.c:3405 __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_trace+0x26d/0x3f0 mm/slub.c:3253 kmalloc include/linux/slab.h:600 [inline] kzalloc include/linux/slab.h:733 [inline] kernfs_fop_open+0x317/0xda0 fs/kernfs/file.c:621 do_dentry_open+0x4a1/0x11f0 fs/open.c:824 do_open fs/namei.c:3520 [inline] path_openat+0x1c71/0x2910 fs/namei.c:3653 do_filp_open+0x1aa/0x400 fs/namei.c:3680 do_sys_openat2+0x16d/0x4c0 fs/open.c:1256 do_sys_open fs/open.c:1272 [inline] __do_sys_openat fs/open.c:1288 [inline] __se_sys_openat fs/open.c:1283 [inline] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1283 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: ffff88807de28280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88807de28300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88807de28380: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff88807de28400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88807de28480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== --- This report is generated by a bot. 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