On Fri, Jul 15, 2016 at 9:03 PM, Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> wrote: > On Tue, Jul 05, 2016 at 01:39:23PM +0200, Dmitry Vyukov wrote: >> 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; > > This open() code is unreachable because the thread argument will only be 0-4, > right? Should this be "case 4"? I am not sure. I think it I just copy-pasted the program that triggered the crash for me. Andrey should have a valid reproducer, in the other thread he said that he can reproduce it. Andrey, did you change 5 to 4? >> } >> 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). > > -- > You received this message because you are subscribed to the Google Groups "syzkaller" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@xxxxxxxxxxxxxxxx. > For more options, visit https://groups.google.com/d/optout. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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