Hello, The following program trigger BUG in expand_downwards (run it in tight parallel loop for a while): // autogenerated by syzkaller (http://github.com/google/syzkaller) #include <pthread.h> #include <stdint.h> #include <string.h> #include <sys/syscall.h> #include <unistd.h> long r[10]; void* thr(void* arg) { switch ((long)arg) { case 0: r[0] = syscall(SYS_mmap, 0x20731000ul, 0x2000ul, 0x2ul, 0x22132ul, 0xfffffffffffffffful, 0x0ul); break; case 1: r[1] = syscall(SYS_mremap, 0x20732000ul, 0x1000ul, 0x3000ul, 0x3ul, 0x2015b000ul, 0); break; case 2: r[2] = syscall(SYS_fanotify_init, 0x20ul, 0x40002ul, 0, 0, 0, 0); break; case 3: r[3] = syscall(SYS_mremap, 0x2015c000ul, 0x1000ul, 0x4000ul, 0x3ul, 0x204eb000ul, 0); break; case 4: r[4] = syscall(SYS_munlock, 0x204eb000ul, 0x4000ul, 0, 0, 0, 0); break; case 5: r[5] = syscall(SYS_mremap, 0x204ec000ul, 0x1000ul, 0x1000ul, 0x3ul, 0x2015d000ul, 0); break; case 6: r[6] = syscall(SYS_mmap, 0x20000000ul, 0x1000ul, 0x3ul, 0x32ul, 0xfffffffffffffffful, 0x0ul); break; case 7: r[7] = syscall(SYS_sigaltstack, 0x204ec000ul, 0x20000000ul, 0, 0, 0, 0); break; case 8: memcpy((void*)0x2015bffa, "\x2e\x2f\x62\x75\x73\x00", 6); r[9] = syscall(SYS_mkdir, 0x2015bffaul, 0x108ul, 0, 0, 0, 0); break; } return 0; } int main() { long i; pthread_t th[9]; srand(getpid()); memset(r, -1, sizeof(r)); for (i = 0; i < 9; i++) { pthread_create(&th[i], 0, thr, (void*)i); usleep(1000); } for (i = 0; i < 9; i++) { pthread_create(&th[i], 0, thr, (void*)i); usleep(rand()%1000); } usleep(10000); return 0; } ===================================== [ BUG: bad unlock balance detected! ] 4.5.0-rc1+ #292 Not tainted ------------------------------------- a.out/7506 is trying to release lock (&anon_vma->rwsem) at: [< inline >] vma_unlock_anon_vma include/linux/rmap.h:123 [<ffffffff816f8e5d>] validate_mm+0x12d/0x850 mm/mmap.c:461 but there are no more locks to release! other info that might help us debug this: 1 lock held by a.out/7506: #0: (&mm->mmap_sem){++++++}, at: [<ffffffff8127dfd7>] __do_page_fault+0x737/0x960 arch/x86/mm/fault.c:1184 stack backtrace: CPU: 1 PID: 7506 Comm: a.out Not tainted 4.5.0-rc1+ #292 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 00000000ffffffff ffff88005d107b50 ffffffff829e79ad ffff8800603b4ce8 ffff88005f15df00 ffffffff816f8e5d ffff88005d107b80 ffffffff81450884 ffff8800603b4ce8 ffff88005f15e720 ffff88005f15e720 00000000ffffffff Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff829e79ad>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [<ffffffff81450884>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3261 [< inline >] __lock_release kernel/locking/lockdep.c:3385 [<ffffffff8145c687>] lock_release+0x937/0xce0 kernel/locking/lockdep.c:3606 [<ffffffff814490ba>] up_write+0x1a/0x60 kernel/locking/rwsem.c:91 [< inline >] vma_unlock_anon_vma include/linux/rmap.h:123 [<ffffffff816f8e5d>] validate_mm+0x12d/0x850 mm/mmap.c:461 [<ffffffff817034be>] expand_downwards+0x19e/0xb30 mm/mmap.c:2283 [<ffffffff81703ecb>] expand_stack+0x7b/0xe0 mm/mmap.c:2338 [<ffffffff8127df88>] __do_page_fault+0x6e8/0x960 arch/x86/mm/fault.c:1217 [<ffffffff8127e358>] trace_do_page_fault+0xe8/0x420 arch/x86/mm/fault.c:1331 [<ffffffff8126f514>] do_async_page_fault+0x14/0xd0 arch/x86/kernel/kvm.c:264 [<ffffffff8645bdf8>] async_page_fault+0x28/0x30 arch/x86/entry/entry_64.S:986 [< inline >] SYSC_sigaltstack kernel/signal.c:3157 [<ffffffff8138600c>] SyS_sigaltstack+0x6c/0x90 kernel/signal.c:3155 [<ffffffff86459ab6>] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 mmap: free gap 1000, correct 0 mm ffff8800603a4e00 mmap ffff88005fc794c0 seqnum 12 task_size 140737488351232 get_unmapped_area ffffffff811af470 mmap_base 140584500215808 mmap_legacy_base 47048170172416 highest_vm_end 140737437655040 pgd ffff88005fc20000 mm_users 2 mm_count 1 nr_ptes 25 nr_pmds 3 map_count 49 hiwater_rss 7 hiwater_vm 813a total_vm 913e locked_vm 2 pinned_vm 0 data_vm 902e exec_vm d1 stack_vm 2a start_code 400000 end_code 4ce986 start_data 6cee90 end_data 6d0d88 start_brk 934000 brk 957000 start_stack 7ffffcf5e660 arg_start 7ffffcf5feae arg_end 7ffffcf5feb6 env_start 7ffffcf5feb6 env_end 7ffffcf5fff0 binfmt ffffffff8797c260 flags cd core_state (null) ioctx_table (null) owner ffff88005d99df00 exe_file ffff880033321680 mmu_notifier_mm (null) flags: 0x0() ------------[ cut here ]------------ kernel BUG at mm/mmap.c:481! invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Modules linked in: CPU: 1 PID: 9534 Comm: a.out Not tainted 4.5.0-rc1+ #292 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff880031522f80 ti: ffff8800314f8000 task.ti: ffff8800314f8000 RIP: 0010:[<ffffffff816f922c>] [<ffffffff816f922c>] validate_mm+0x4fc/0x850 RSP: 0018:ffff8800314ffc60 EFLAGS: 00010286 RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffffed000629ff22 RBP: ffff8800314ffcc8 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000003 R11: 1ffffffff12e43c4 R12: 0000000000000031 R13: 0000000000000000 R14: 00007ffffcfa4000 R15: dffffc0000000000 FS: 00007fdc59313700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00000000204ec000 CR3: 000000005fc20000 CR4: 00000000000006e0 Stack: 0000000000486f70 ffff8800603a4e60 ffff8800603a4e00 0000003100000001 0000000000000000 0000000000041000 ffff88005fc78538 ffff88005fc78530 ffff880032870a60 0000000000000000 ffff880031e61e00 000000001f6a9000 Call Trace: [<ffffffff817034be>] expand_downwards+0x19e/0xb30 mm/mmap.c:2283 [<ffffffff81703ecb>] expand_stack+0x7b/0xe0 mm/mmap.c:2338 [<ffffffff8127df88>] __do_page_fault+0x6e8/0x960 arch/x86/mm/fault.c:1217 [<ffffffff8127e358>] trace_do_page_fault+0xe8/0x420 arch/x86/mm/fault.c:1331 [<ffffffff8126f514>] do_async_page_fault+0x14/0xd0 arch/x86/kernel/kvm.c:264 [<ffffffff8645bdf8>] async_page_fault+0x28/0x30 arch/x86/entry/entry_64.S:986 [< inline >] SYSC_sigaltstack kernel/signal.c:3157 [<ffffffff8138600c>] SyS_sigaltstack+0x6c/0x90 kernel/signal.c:3155 [<ffffffff86459ab6>] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 Code: 58 60 44 39 e3 74 73 e8 03 0f e7 ff 44 89 e2 89 de 48 c7 c7 a0 dc 5a 86 e8 e7 c3 f4 ff e8 ed 0e e7 ff 48 8b 7d a8 e8 24 00 fe ff <0f> 0b e8 dd 0e e7 ff 8b 55 b4 44 89 e6 48 c7 c7 40 dc 5a 86 e8 RIP [<ffffffff816f922c>] validate_mm+0x4fc/0x850 mm/mmap.c:481 RSP <ffff8800314ffc60> ---[ end trace 5282aed32b3391b4 ]--- And there seems to be some locking issue in validate_mm. 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