On Tue, Apr 23, 2019 at 09:30:22AM -0700, Zubin Mithra wrote:
Hello,
Syzkaller has triggered a kernel WARNING with the following stacktrace when fuzzing a 4.14 kernel.
Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xb7/0x107 lib/dump_stack.c:53 panic+0x1c9/0x3ae kernel/panic.c:181 __warn+0x160/0x1a8 kernel/panic.c:543 report_bug+0x123/0x18b lib/bug.c:186 fixup_bug+0x3e/0x77 arch/x86/kernel/traps.c:177 do_error_trap+0xdd/0x1e6 arch/x86/kernel/traps.c:295 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:944 do_blockdev_direct_IO+0x1b08/0x1b95 fs/direct-io.c:1373 ext4_direct_IO_write fs/ext4/inode.c:3696 [inline] ext4_direct_IO+0x8de/0xdad fs/ext4/inode.c:3826 generic_file_direct_write+0x223/0x36b mm/filemap.c:2927 __generic_file_write_iter+0x12f/0x2f8 mm/filemap.c:3106 ext4_file_write_iter+0x97d/0xade fs/ext4/file.c:264 call_write_iter include/linux/fs.h:1782 [inline] do_iter_readv_writev+0x1e4/0x27c fs/read_write.c:678 do_iter_write+0x136/0x18f fs/read_write.c:957 vfs_iter_write+0x81/0x98 fs/read_write.c:970 iter_file_splice_write+0x4dc/0x7a6 fs/splice.c:749 do_splice_from fs/splice.c:851 [inline] direct_splice_actor+0x11e/0x129 fs/splice.c:1018 splice_direct_to_actor+0x342/0x5b0 fs/splice.c:973 do_splice_direct+0x180/0x1ff fs/splice.c:1061 do_sendfile+0x3e6/0x61c fs/read_write.c:1438 SYSC_sendfile64 fs/read_write.c:1499 [inline] SyS_sendfile64+0xe9/0x128 fs/read_write.c:1485 do_syscall_64+0x203/0x241 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x42/0xb7
Could the following patch be applied in order to v4.14.y(The patch is present in v4.19.y)? 5a9d929d6e13 ("iomap: report collisions between directio and buffered writes to userspace")
That patch only teaches the kernel to emit warnings in dmesg when programs mix directio and buffered writes. It doesn't fix any buggy directio usage. Someone on the ext4 list [cc'd] might know more about this.
--D
Tests run:
- Chrome OS tryjobs
- Syzkaller reproducer
Thanks,
- Zubin