[+ashmem maintainers] On Sun, Apr 29, 2018 at 10:00:03AM -0700, syzbot wrote: > Hello, > > syzbot hit the following crash on upstream commit > cdface5209349930ae1b51338763c8e029971b97 (Sun Apr 29 03:07:21 2018 +0000) > Merge tag 'for_linus_stable' of > git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 > syzbot dashboard link: > https://syzkaller.appspot.com/bug?extid=148c2885d71194f18d28 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5054004375584768 > syzkaller reproducer: > https://syzkaller.appspot.com/x/repro.syz?id=6438048191479808 > Raw console output: > https://syzkaller.appspot.com/x/log.txt?id=5404215203594240 > Kernel config: > https://syzkaller.appspot.com/x/.config?id=7043958930931867332 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+148c2885d71194f18d28@xxxxxxxxxxxxxxxxxxxxxxxxx > It will help syzbot understand when the bug is fixed. See footer for > details. > If you forward the report, please keep this part and the footer. > > 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 > 4.17.0-rc2+ #23 Not tainted > ------------------------------------------------------ > syz-executor715/4492 is trying to acquire lock: > (ptrval) (sb_writers#6){.+.+}, at: file_start_write > include/linux/fs.h:2718 [inline] > (ptrval) (sb_writers#6){.+.+}, at: vfs_fallocate+0x5be/0x8d0 > fs/open.c:318 > > but task is already holding lock: > (ptrval) (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xac/0x560 > drivers/staging/android/ashmem.c:440 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #3 (ashmem_mutex){+.+.}: > __mutex_lock_common kernel/locking/mutex.c:756 [inline] > __mutex_lock+0x16d/0x17f0 kernel/locking/mutex.c:893 > mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 > ashmem_mmap+0x53/0x460 drivers/staging/android/ashmem.c:361 > call_mmap include/linux/fs.h:1789 [inline] > mmap_region+0xd13/0x1820 mm/mmap.c:1723 > do_mmap+0xc79/0x11d0 mm/mmap.c:1494 > do_mmap_pgoff include/linux/mm.h:2237 [inline] > vm_mmap_pgoff+0x1fb/0x2a0 mm/util.c:357 > ksys_mmap_pgoff+0x4c9/0x640 mm/mmap.c:1544 > __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+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > -> #2 (&mm->mmap_sem){++++}: > __might_fault+0x155/0x1e0 mm/memory.c:4555 > _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:3378 [inline] > dir_emit_dots include/linux/fs.h:3389 [inline] > dcache_readdir+0x13a/0x620 fs/libfs.c:192 > iterate_dir+0x4b0/0x5d0 fs/readdir.c:51 > __do_sys_getdents fs/readdir.c:231 [inline] > __se_sys_getdents fs/readdir.c:212 [inline] > __x64_sys_getdents+0x293/0x4e0 fs/readdir.c:212 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > -> #1 (&sb->s_type->i_mutex_key#11){++++}: > down_write+0x87/0x120 kernel/locking/rwsem.c:70 > inode_lock include/linux/fs.h:713 [inline] > do_last fs/namei.c:3274 [inline] > path_openat+0x123b/0x4e20 fs/namei.c:3501 > do_filp_open+0x249/0x350 fs/namei.c:3535 > do_sys_open+0x56f/0x740 fs/open.c:1093 > __do_sys_open fs/open.c:1111 [inline] > __se_sys_open fs/open.c:1106 [inline] > __x64_sys_open+0x7e/0xc0 fs/open.c:1106 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > -> #0 (sb_writers#6){.+.+}: > lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 > percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 > [inline] > percpu_down_read include/linux/percpu-rwsem.h:59 [inline] > __sb_start_write+0x1e9/0x300 fs/super.c:1385 > file_start_write include/linux/fs.h:2718 [inline] > vfs_fallocate+0x5be/0x8d0 fs/open.c:318 > ashmem_shrink_scan+0x1f1/0x560 drivers/staging/android/ashmem.c:447 > ashmem_ioctl+0x3bf/0x13a0 drivers/staging/android/ashmem.c:789 > vfs_ioctl fs/ioctl.c:46 [inline] > file_ioctl fs/ioctl.c:500 [inline] > do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 > ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 > __do_sys_ioctl fs/ioctl.c:708 [inline] > __se_sys_ioctl fs/ioctl.c:706 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > other info that might help us debug this: > > Chain exists of: > sb_writers#6 --> &mm->mmap_sem --> ashmem_mutex > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(ashmem_mutex); > lock(&mm->mmap_sem); > lock(ashmem_mutex); > lock(sb_writers#6); > > *** DEADLOCK *** > > 1 lock held by syz-executor715/4492: > #0: (ptrval) (ashmem_mutex){+.+.}, at: > ashmem_shrink_scan+0xac/0x560 drivers/staging/android/ashmem.c:440 > > stack backtrace: > CPU: 1 PID: 4492 Comm: syz-executor715 Not tainted 4.17.0-rc2+ #23 > 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+0x1b9/0x294 lib/dump_stack.c:113 > print_circular_bug.isra.36.cold.54+0x1bd/0x27d > kernel/locking/lockdep.c:1223 > check_prev_add kernel/locking/lockdep.c:1863 [inline] > check_prevs_add kernel/locking/lockdep.c:1976 [inline] > validate_chain kernel/locking/lockdep.c:2417 [inline] > __lock_acquire+0x343e/0x5140 kernel/locking/lockdep.c:3431 > lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 > percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline] > percpu_down_read include/linux/percpu-rwsem.h:59 [inline] > __sb_start_write+0x1e9/0x300 fs/super.c:1385 > file_start_write include/linux/fs.h:2718 [inline] > vfs_fallocate+0x5be/0x8d0 fs/open.c:318 > ashmem_shrink_scan+0x1f1/0x560 drivers/staging/android/ashmem.c:447 > ashmem_ioctl+0x3bf/0x13a0 drivers/staging/android/ashmem.c:789 > vfs_ioctl fs/ioctl.c:46 [inline] > file_ioctl fs/ioctl.c:500 [inline] > do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 > ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 > __do_sys_ioctl fs/ioctl.c:708 [inline] > __se_sys_ioctl fs/ioctl.c:706 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x440179 > RSP: 002b:00007ffc165d4a28 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 6873612f7665642f RCX: 0000000000440179 > RDX: 0000000000000000 RSI: 000000000000770a RDI: 0000000000000004 > RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000004 R11: 0000000000000217 R12: 00000000004016a0 > R13: 0000000000401730 R14: 0000000000000000 R15: 0000000000000000 > random: crng init done > > > --- > This bug is generated by a dumb bot. It may contain errors. > See https://goo.gl/tpsmEJ for details. > Direct all questions to syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. > If you forgot to add the Reported-by tag, once the fix for this bug is > merged > into any tree, please reply to this email with: > #syz fix: exact-commit-title > If you want to test a patch for this bug, please reply with: > #syz test: git://repo/address.git branch > and provide the patch inline or as an attachment. > To mark this as a duplicate of another syzbot report, please reply with: > #syz dup: exact-subject-of-another-report > If it's a one-off invalid bug report, please reply with: > #syz invalid > Note: if the crash happens again, it will cause creation of a new bug > report. > Note: all commands must start from beginning of the line in the email body. Looks like yet another locking bug in ashmem. ashmem_mutex normally ranks below mmap_sem, but ashmem_shrink_scan() inverts that order, via the file_start_write() in vfs_fallocate(). - Eric _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
