Hello, The following program triggers GPF in find_get_pages_tag if run in parallel loop for minutes: kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Modules linked in: CPU: 2 PID: 301 Comm: a.out Tainted: G W 4.7.0-rc5+ #28 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff880063d12440 ti: ffff880067350000 task.ti: ffff880067350000 RIP: 0010:[<ffffffff816951a4>] [< inline >] radix_tree_next_slot include/linux/radix-tree.h:473 [<ffffffff816951a4>] find_get_pages_tag+0x334/0x930 mm/filemap.c:1452 RSP: 0018:ffff880067357840 EFLAGS: 00010202 RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffff880063d12c80 RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 0000000000000008 RBP: ffff880067357910 R08: 0000000000000002 R09: 0000000000000000 R10: 0000000000000000 R11: ffffffff89f06360 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000000 R15: ffffed0007058ee5 FS: 00007f56e017c700(0000) GS:ffff88006d400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f56df97ae78 CR3: 0000000063d9e000 CR4: 00000000000006e0 Stack: ffffffff81694efc ffff8800673578a8 0000010267357860 ffff880067357a50 ffff880065986aa0 1ffff1000ce6af11 0000000e00000000 ffff880067357a00 0000000000000003 0000000041b58ab3 ffffffff87e2a722 ffffffff81694e70 Call Trace: [<ffffffff816cd91a>] pagevec_lookup_tag+0x3a/0x80 mm/swap.c:960 [<ffffffff81ab4231>] mpage_prepare_extent_to_map+0x321/0xa90 fs/ext4/inode.c:2516 [<ffffffff81ac883e>] ext4_writepages+0x10be/0x2b20 fs/ext4/inode.c:2736 [<ffffffff816c99c7>] do_writepages+0x97/0x100 mm/page-writeback.c:2364 [<ffffffff8169bee8>] __filemap_fdatawrite_range+0x248/0x2e0 mm/filemap.c:300 [<ffffffff8169c371>] filemap_write_and_wait_range+0x121/0x1b0 mm/filemap.c:490 [<ffffffff81aa584d>] ext4_sync_file+0x34d/0xdb0 fs/ext4/fsync.c:115 [<ffffffff818b667a>] vfs_fsync_range+0x10a/0x250 fs/sync.c:195 [< inline >] vfs_fsync fs/sync.c:209 [<ffffffff818b6832>] do_fsync+0x42/0x70 fs/sync.c:219 [< inline >] SYSC_fdatasync fs/sync.c:232 [<ffffffff818b6f89>] SyS_fdatasync+0x19/0x20 fs/sync.c:230 [<ffffffff86a94e00>] entry_SYSCALL_64_fastpath+0x23/0xc1 arch/x86/entry/entry_64.S:207 Code: 85 70 ff ff ff 49 d1 ec 4d 85 e4 4c 89 65 a8 74 65 e8 51 06 f0 ff 49 8d 7e 08 48 be 00 00 00 00 00 fc ff df 48 89 f8 48 c1 e8 03 <80> 3c 30 00 0f 85 9c 05 00 00 4d 8b 6e 08 4c 89 eb 83 e3 03 48 RIP [< inline >] radix_tree_next_slot include/linux/radix-tree.h:473 RIP [<ffffffff816951a4>] find_get_pages_tag+0x334/0x930 mm/filemap.c:1452 RSP <ffff880067357840> ---[ end trace 33a0cc4dd9a49a67 ]--- // autogenerated by syzkaller (http://github.com/google/syzkaller) #include <pthread.h> #include <stdint.h> #include <string.h> #include <stdio.h> #include <sys/syscall.h> #include <unistd.h> int fd; char buf[8192]; char filename[256]; void* thr(void* arg) { switch ((long)arg) { case 0: write(fd, buf, 0x1001ul); break; case 1: fdatasync(fd); break; case 2: ftruncate(fd, 2); break; case 3: write(fd, buf, 0x20ul); break; case 5: fd = open(filename, 0x50042ul, 0x41ul); break; } return 0; } int main() { long i; pthread_t th[10]; srand(getpid()); sprintf(filename, "./file%d", getpid()); fd = open(filename, 0x50042ul, 0x41ul); for (i = 0; i < 10; i++) { pthread_create(&th[i], 0, thr, (void*)(i % 5)); usleep(rand() % 10); } for (i = 0; i < 10; i++) pthread_join(th[i], 0); unlink(filename); return 0; } The faulting instruction is: ffffffff816951a4: 80 3c 30 00 cmpb $0x0,(%rax,%rsi,1) So this is KASAN shadow check for NULL address. The previous taint is not relevant, it is: [ 74.786477] ------------[ cut here ]------------ [ 74.786885] WARNING: CPU: 2 PID: 717 at lib/stackdepot.c:119 depot_save_stack+0x34f/0x5b0 [ 74.787196] Stack depot reached limit capacity On commit 1a0a02d1efa066001fd315c1b4df583d939fa2c4 (Jun 30). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>