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Fri, 10 Aug 2018 04:59:02 -0700 (PDT) Date: Fri, 10 Aug 2018 04:59:02 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <0000000000004024240573137822@google.com> Subject: possible deadlock in shmem_fallocate (2) From: syzbot To: hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, syzbot found the following crash on: HEAD commit: 4110b42356f3 Add linux-next specific files for 20180810 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1411d6e2400000 kernel config: https://syzkaller.appspot.com/x/.config?x=1d80606e3795a4f5 dashboard link: https://syzkaller.appspot.com/bug?extid=4b8b031b89e6b96c4b2e compiler: gcc (GCC) 8.0.1 20180413 (experimental) syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=175052f8400000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11873622400000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4b8b031b89e6b96c4b2e@syzkaller.appspotmail.com random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) ====================================================== WARNING: possible circular locking dependency detected 4.18.0-rc8-next-20180810+ #36 Not tainted ------------------------------------------------------ syz-executor900/4483 is trying to acquire lock: 00000000d2bfc8fe (&sb->s_type->i_mutex_key#9){++++}, at: inode_lock include/linux/fs.h:765 [inline] 00000000d2bfc8fe (&sb->s_type->i_mutex_key#9){++++}, at: shmem_fallocate+0x18b/0x12e0 mm/shmem.c:2602 but task is already holding lock: 0000000025208078 (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 drivers/staging/android/ashmem.c:448 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (ashmem_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x171/0x1700 kernel/locking/mutex.c:1073 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1088 ashmem_mmap+0x55/0x520 drivers/staging/android/ashmem.c:361 call_mmap include/linux/fs.h:1844 [inline] mmap_region+0xf27/0x1c50 mm/mmap.c:1762 do_mmap+0xa10/0x1220 mm/mmap.c:1535 do_mmap_pgoff include/linux/mm.h:2298 [inline] vm_mmap_pgoff+0x213/0x2c0 mm/util.c:357 ksys_mmap_pgoff+0x4da/0x660 mm/mmap.c:1585 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline] __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&mm->mmap_sem){++++}: __might_fault+0x155/0x1e0 mm/memory.c:4568 _copy_to_user+0x30/0x110 lib/usercopy.c:25 copy_to_user include/linux/uaccess.h:155 [inline] filldir+0x1ea/0x3a0 fs/readdir.c:196 dir_emit_dot include/linux/fs.h:3464 [inline] dir_emit_dots include/linux/fs.h:3475 [inline] dcache_readdir+0x13a/0x620 fs/libfs.c:193 iterate_dir+0x48b/0x5d0 fs/readdir.c:51 __do_sys_getdents fs/readdir.c:231 [inline] __se_sys_getdents fs/readdir.c:212 [inline] __x64_sys_getdents+0x29f/0x510 fs/readdir.c:212 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sb->s_type->i_mutex_key#9){++++}: lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924 down_write+0x8f/0x130 kernel/locking/rwsem.c:70 inode_lock include/linux/fs.h:765 [inline] shmem_fallocate+0x18b/0x12e0 mm/shmem.c:2602 ashmem_shrink_scan+0x236/0x630 drivers/staging/android/ashmem.c:455 ashmem_ioctl+0x3ae/0x13a0 drivers/staging/android/ashmem.c:797 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702 __do_sys_ioctl fs/ioctl.c:709 [inline] __se_sys_ioctl fs/ioctl.c:707 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &sb->s_type->i_mutex_key#9 --> &mm->mmap_sem --> ashmem_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ashmem_mutex); lock(&mm->mmap_sem); lock(ashmem_mutex); lock(&sb->s_type->i_mutex_key#9); *** DEADLOCK *** 1 lock held by syz-executor900/4483: #0: 0000000025208078 (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 drivers/staging/android/ashmem.c:448 stack backtrace: CPU: 1 PID: 4483 Comm: syz-executor900 Not tainted 4.18.0-rc8-next-20180810+ #36 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+0x1c9/0x2b4 lib/dump_stack.c:113 print_circular_bug.isra.37.cold.58+0x1bd/0x27d kernel/locking/lockdep.c:1227 check_prev_add kernel/locking/lockdep.c:1867 [inline] check_prevs_add kernel/locking/lockdep.c:1980 [inline] validate_chain kernel/locking/lockdep.c:2421 [inline] __lock_acquire+0x3449/0x5020 kernel/locking/lockdep.c:3435 lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924 down_write+0x8f/0x130 kernel/locking/rwsem.c:70 inode_lock include/linux/fs.h:765 [inline] shmem_fallocate+0x18b/0x12e0 mm/shmem.c:2602 ashmem_shrink_scan+0x236/0x630 drivers/staging/android/ashmem.c:455 ashmem_ioctl+0x3ae/0x13a0 drivers/staging/android/ashmem.c:797 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702 __do_sys_ioctl fs/ioctl.c:709 [inline] __se_sys_ioctl fs/ioctl.c:707 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x440099 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fff3613dbf8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440099 RDX: 00000 --- This bug 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 bug report. See: https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches