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Sun, 06 Dec 2020 10:03:09 -0800 (PST) Date: Sun, 06 Dec 2020 10:03:09 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <000000000000b73ccc05b5cf8558@google.com> Subject: possible deadlock in hugetlb_cow From: syzbot To: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mike.kravetz@oracle.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, syzbot found the following issue on: HEAD commit: 509a1542 Merge tag '5.10-rc6-smb3-fixes' of git://git.samb.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1694d673500000 kernel config: https://syzkaller.appspot.com/x/.config?x=e49433cfed49b7d9 dashboard link: https://syzkaller.appspot.com/bug?extid=5eee4145df3c15e96625 compiler: gcc (GCC) 10.1.0-syz 20200507 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f16b3b500000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107c8379500000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+5eee4145df3c15e96625@syzkaller.appspotmail.com ============================================ WARNING: possible recursive locking detected 5.10.0-rc6-syzkaller #0 Not tainted -------------------------------------------- syz-executor036/9857 is trying to acquire lock: ffff888011675698 (&hugetlbfs_i_mmap_rwsem_key){++++}-{3:3}, at: i_mmap_lock_write include/linux/fs.h:493 [inline] ffff888011675698 (&hugetlbfs_i_mmap_rwsem_key){++++}-{3:3}, at: unmap_ref_private mm/hugetlb.c:4019 [inline] ffff888011675698 (&hugetlbfs_i_mmap_rwsem_key){++++}-{3:3}, at: hugetlb_cow+0xedf/0x15f0 mm/hugetlb.c:4110 but task is already holding lock: ffff888011675698 (&hugetlbfs_i_mmap_rwsem_key){++++}-{3:3}, at: i_mmap_lock_read include/linux/fs.h:508 [inline] ffff888011675698 (&hugetlbfs_i_mmap_rwsem_key){++++}-{3:3}, at: hugetlb_fault+0x26c/0x2330 mm/hugetlb.c:4485 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&hugetlbfs_i_mmap_rwsem_key); lock(&hugetlbfs_i_mmap_rwsem_key); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by syz-executor036/9857: #0: ffff88801aed8128 (&mm->mmap_lock#2){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:56 [inline] #0: ffff88801aed8128 (&mm->mmap_lock#2){++++}-{3:3}, at: do_user_addr_fault+0x25c/0xb40 arch/x86/mm/fault.c:1313 #1: ffff888011675698 (&hugetlbfs_i_mmap_rwsem_key){++++}-{3:3} , at: i_mmap_lock_read include/linux/fs.h:508 [inline] , at: hugetlb_fault+0x26c/0x2330 mm/hugetlb.c:4485 #2: ffff8880147fe2a8 (&hugetlb_fault_mutex_table[i]){+.+.}-{3:3}, at: hugetlb_fault+0x368/0x2330 mm/hugetlb.c:4499 stack backtrace: CPU: 0 PID: 9857 Comm: syz-executor036 Not tainted 5.10.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x107/0x163 lib/dump_stack.c:118 print_deadlock_bug kernel/locking/lockdep.c:2761 [inline] check_deadlock kernel/locking/lockdep.c:2804 [inline] validate_chain kernel/locking/lockdep.c:3595 [inline] __lock_acquire.cold+0x15e/0x3b0 kernel/locking/lockdep.c:4832 lock_acquire kernel/locking/lockdep.c:5437 [inline] lock_acquire+0x29d/0x740 kernel/locking/lockdep.c:5402 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 i_mmap_lock_write include/linux/fs.h:493 [inline] unmap_ref_private mm/hugetlb.c:4019 [inline] hugetlb_cow+0xedf/0x15f0 mm/hugetlb.c:4110 hugetlb_fault+0x155c/0x2330 mm/hugetlb.c:4562 handle_mm_fault+0x11c3/0x55d0 mm/memory.c:4605 do_user_addr_fault+0x55b/0xb40 arch/x86/mm/fault.c:1372 handle_page_fault arch/x86/mm/fault.c:1429 [inline] exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1485 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:583 RIP: 0033:0x401d0f Code: 00 00 31 c0 e8 52 a8 04 00 f0 83 2d 0a e3 2f 00 01 4c 89 e7 e8 42 ff ff ff eb b1 85 c0 75 ea b9 6e 00 00 00 4c 89 ef 4c 89 f6 48 a5 ba 04 00 00 00 0f b7 06 be 00 0f 00 20 66 89 07 31 c0 bf RSP: 002b:00007fc848488db0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000700028 RCX: 000000000000006e RDX: 00000000000f4240 RSI: 00000000004b4a00 RDI: 0000000020000f00 RBP: 0000000000700020 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000070002c R13: 0000000020000f00 R14: 00000000004b4a00 R15: 20c49ba5e353f7cf --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches