syzbot has found a reproducer for the following crash on: HEAD commit: 763dede1 Merge tag 'for-linus-5.7-rc1' of git://git.kernel.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17731b0be00000 kernel config: https://syzkaller.appspot.com/x/.config?x=12205d036cec317f dashboard link: https://syzkaller.appspot.com/bug?extid=a8c70b7f3579fc0587dc compiler: gcc (GCC) 9.0.0 20181231 (experimental) userspace arch: i386 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=135855cde00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=149ea07de00000 The bug was bisected to: commit 71335f37c5e8ec9225285206f7f875057b9737ad Author: Peter Xu <peterx@xxxxxxxxxx> Date: Thu Apr 2 04:08:53 2020 +0000 mm/gup: allow to react to fatal signals bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17dba9b3e00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=143ba9b3e00000 console output: https://syzkaller.appspot.com/x/log.txt?x=103ba9b3e00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+a8c70b7f3579fc0587dc@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 71335f37c5e8 ("mm/gup: allow to react to fatal signals") ===================================== WARNING: bad unlock balance detected! 5.6.0-syzkaller #0 Not tainted ------------------------------------- syz-executor151/7052 is trying to release lock (&mm->mmap_sem) at: [<ffffffff819fbf60>] __get_user_pages_locked mm/gup.c:1366 [inline] [<ffffffff819fbf60>] __get_user_pages_remote mm/gup.c:1831 [inline] [<ffffffff819fbf60>] __get_user_pages_remote+0x540/0x740 mm/gup.c:1806 but there are no more locks to release! other info that might help us debug this: no locks held by syz-executor151/7052. stack backtrace: CPU: 0 PID: 7052 Comm: syz-executor151 Not tainted 5.6.0-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+0x188/0x20d lib/dump_stack.c:118 __lock_release kernel/locking/lockdep.c:4633 [inline] lock_release+0x586/0x800 kernel/locking/lockdep.c:4941 up_read+0x79/0x750 kernel/locking/rwsem.c:1573 __get_user_pages_locked mm/gup.c:1366 [inline] __get_user_pages_remote mm/gup.c:1831 [inline] __get_user_pages_remote+0x540/0x740 mm/gup.c:1806 pin_user_pages_remote+0x67/0xa0 mm/gup.c:2897 process_vm_rw_single_vec mm/process_vm_access.c:108 [inline] process_vm_rw_core.isra.0+0x423/0x940 mm/process_vm_access.c:218 compat_process_vm_rw+0x21f/0x240 mm/process_vm_access.c:343 __do_compat_sys_process_vm_writev mm/process_vm_access.c:370 [inline] __se_compat_sys_process_vm_writev mm/process_vm_access.c:363 [inline] __ia32_compat_sys_process_vm_writev+0xdc/0x1b0 mm/process_vm_access.c:363 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline] do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 ------------[ cut here ]------------ DEBUG_RWSEMS_WARN_ON(tmp < 0): count = 0xffffffffffffff00, magic = 0xffff88809e2392f8, owner = 0x3, curr 0xffff88809a6c6240, list empty WARNING: CPU: 1 PID: 7052 at kernel/locking/rwsem.c:1435 __up_read kernel/locking/rwsem.c:1435 [inline] WARNING: CPU: 1 PID: 7052 at kernel/locking/rwsem.c:1435 up_read+0x5f9/0x750 kernel/locking/rwsem.c:1574
