Sasha Levin <sasha.levin@xxxxxxxxxx> writes: > Hi all, > > While fuzzing with trinity inside a KVM tools guest running the latest -next > kernel, I've stumbled on the following spew: Indeed this is a pure bug. Race between write and fcntl(F_SETFL) which toggling O_DIRECT. So even if we started with buffered path we may endup in direct one :) See my testcase: http://marc.info/?l=linux-ext4&m=141284883914726&w=2 Unfortunately f_flags guarded by filp->f_lock so it looks like we can not use generic __generic_file_write_iter() and need specific one which use precached o_direct status. > > [ 409.233952] kernel BUG at fs/ext4/inode.c:2959! > [ 409.234761] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN > [ 409.237192] Dumping ftrace buffer: > [ 409.238424] (ftrace buffer empty) > [ 409.239664] Modules linked in: > [ 409.240706] CPU: 18 PID: 14016 Comm: trinity-c27 Not tainted 3.17.0-next-20141008-sasha-00051-g78b3c93-dirty #1364 > [ 409.242724] task: ffff88032bb00000 ti: ffff8802e78f8000 task.ti: ffff8802e78f8000 > [ 409.242724] RIP: ext4_direct_IO (fs/ext4/inode.c:2959 fs/ext4/inode.c:3098) > [ 409.242724] RSP: 0018:ffff8802e78fbb98 EFLAGS: 00010246 > [ 409.242724] RAX: ffffda005cf1f7cf RBX: ffff88015f72f2f0 RCX: 0000000000000007 > [ 409.242724] RDX: dfffe90000000000 RSI: 1ffff1002e58c5ef RDI: ffff8802e78fbe78 > [ 409.242724] RBP: ffff8802e78fbc28 R08: dfffe90000000001 R09: ffff8802e78fbe5f > [ 409.242724] R10: 1ffff1005cf1f7cb R11: 0000000000000001 R12: ffff8802e78fbe60 > [ 409.242724] R13: 000000000000000d R14: ffff8802e78fbc60 R15: ffff88015f72f2f0 > [ 409.242724] FS: 0000000000798860(0063) GS:ffff880851c00000(0000) knlGS:0000000000000000 > [ 409.242724] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [ 409.242724] CR2: 0000000002bd70f8 CR3: 000000032b542000 CR4: 00000000000006a0 > [ 409.242724] Stack: > [ 409.242724] ffff88017380a1e8 0000000000000000 ffff8802e78fbbf8 ffffffff9937c5ff > [ 409.242724] ffff88015f72f318 7fffffffffffffff 0000000000000000 ffff8802e78fbe78 > [ 409.242724] ffff88015f72f2f0 0000000000000000 000000000000000d 000000015f72f2f0 > [ 409.242724] Call Trace: > [ 409.242724] ? __filemap_fdatawrite_range (mm/filemap.c:288) > [ 409.242724] generic_file_direct_write (mm/filemap.c:2413) > [ 409.242724] __generic_file_write_iter (mm/filemap.c:2595) > [ 409.242724] ext4_file_write_iter (fs/ext4/file.c:176) > [ 409.242724] ? get_parent_ip (kernel/sched/core.c:2606) > [ 409.242724] ? iov_iter_init (mm/iov_iter.c:442) > [ 409.242724] new_sync_write (fs/read_write.c:478) > [ 409.242724] vfs_write (fs/read_write.c:534) > [ 409.242724] SyS_pwrite64 (fs/read_write.c:627 fs/read_write.c:614) > [ 409.242724] tracesys_phase2 (arch/x86/kernel/entry_64.S:529) > [ 409.242724] Code: 00 00 65 8b 04 25 58 cb 00 00 a9 ff ff ff 7f 0f 85 94 fb ff ff e8 c1 cf ff ff f6 c4 02 0f 84 86 fb ff ff e9 5d fd ff ff 0f 1f 00 <0f> 0b e8 c9 4c c9 ff 84 c0 0f 84 85 fc ff ff 48 c7 c7 80 63 58 > All code > ======== > 0: 00 00 add %al,(%rax) > 2: 65 8b 04 25 58 cb 00 mov %gs:0xcb58,%eax > 9: 00 > a: a9 ff ff ff 7f test $0x7fffffff,%eax > f: 0f 85 94 fb ff ff jne 0xfffffffffffffba9 > 15: e8 c1 cf ff ff callq 0xffffffffffffcfdb > 1a: f6 c4 02 test $0x2,%ah > 1d: 0f 84 86 fb ff ff je 0xfffffffffffffba9 > 23: e9 5d fd ff ff jmpq 0xfffffffffffffd85 > 28: 0f 1f 00 nopl (%rax) > 2b:* 0f 0b ud2 <-- trapping instruction > 2d: e8 c9 4c c9 ff callq 0xffffffffffc94cfb > 32: 84 c0 test %al,%al > 34: 0f 84 85 fc ff ff je 0xfffffffffffffcbf > 3a: 48 c7 c7 80 63 58 00 mov $0x586380,%rdi > > Code starting with the faulting instruction > =========================================== > 0: 0f 0b ud2 > 2: e8 c9 4c c9 ff callq 0xffffffffffc94cd0 > 7: 84 c0 test %al,%al > 9: 0f 84 85 fc ff ff je 0xfffffffffffffc94 > f: 48 c7 c7 80 63 58 00 mov $0x586380,%rdi > [ 409.242724] RIP ext4_direct_IO (fs/ext4/inode.c:2959 fs/ext4/inode.c:3098) > [ 409.242724] RSP <ffff8802e78fbb98> > > Thanks, > Sasha > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
Attachment:
pgprD65oNZFuI.pgp
Description: PGP signature
