Re: [PATCH v4 4/4] generic: mmap write readonly DAX file

Ross Zwisler
2017-04-18T17:05:10Z

On Mon, Apr 17, 2017 at 03:14:15PM +0800, Xiong Zhou wrote:
> Regression case that one can write to read-only
> file in a DAX mountpoint.
>
> Signed-off-by: Xiong Zhou <xzhou@redhat.com>

Yep, this test works fine in my setup. It fails for me, as expected, with
v4.10.0, and passes as expected with v4.10.3. I've added a few small comments
below, but with those addressed you can add:

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>

> +int
> +main(int argc, char **argv)
> +{
> + int fd, pfd, ret;
> + char *buf;
> + /* gcc -O2 will optimize foo's storage, preventing
> + * reproduce this issue.
> + * foo is never actually used after fault in value stored.
> + */
> + volatile char foo __attribute__((__unused__));
> + int pagesize = getpagesize();
> +
> + if (argc < 2) {
> + printf("Usage: %s <file> <pmem file>\n", basename(argv[0]));
> + exit(0);
> + }
> +
> + fd = open(argv[1], O_RDONLY|O_DIRECT);
> + if (fd < 0)
> + err_exit("open");
> +
> + pfd = open(argv[2], O_RDONLY);
> + if (pfd < 0)
> + err_exit("pmem open");
> +
> + buf = mmap(NULL, pagesize, PROT_READ, MAP_SHARED, pfd, 0);
> + if (buf == MAP_FAILED)
> + err_exit("mmap");
> +
> + /*
> + * Read from the DAX mmap to populate the first page in the
> + * address_space with a read-only mapping.
> + */
> + foo = *buf;
> +
> + /*
> + * Now write to the DAX mmap. This *should* fail, but if the bug is
> + * present in __get_user_pages_fast(), it will succeed.
> + */
> + ret = read(fd, buf, pagesize);
> + if (ret != pagesize)
> + err_exit("read");
> +
> + ret = msync(buf, pagesize, MS_SYNC);
> + if (ret != 0)
> + err_exit("msync");
> +
> + ret = munmap(buf, pagesize);
> + if (ret < 0)
> + err_exit("munmap");
> +
> + ret = close(fd);
> + if (ret < 0)
> + err_exit("clsoe fd");
close

> diff --git a/tests/generic/424 b/tests/generic/424
> new file mode 100755
> index 0000000..f73e08a
> --- /dev/null
> +++ b/tests/generic/424
> @@ -0,0 +1,92 @@
> +#! /bin/bash
> +# FS QA Test 424
> +#
> +# This is a regression test for kernel commit
> +# ef947b2 x86, mm: fix gup_pte_range() vs DAX mappings
> +# created by Jeffrey Moyer <jmoyer@redhat.com>
> +#
> +# This is reproducible only when testing on pmem device
> +# which is configured in "memory mode", not in "raw mode".
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2017 Red Hat. All Rights Reserved.
> +#
> +# This program is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU General Public License as
> +# published by the Free Software Foundation.
> +#
> +# This program is distributed in the hope that it would be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program; if not, write the Free Software Foundation,
> +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> +#-----------------------------------------------------------------------
> +#
> +
> +seq=`basename $0`
> +seqres=$RESULT_DIR/$seq
> +echo "QA output created by $seq"
> +
> +here=`pwd`
> +tmp=/tmp/$$
> +status=1 # failure is the default!
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +_cleanup()
> +{
> + cd /
> + rm -rf $tmp.*
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# Modify as appropriate.
> +_supported_fs generic
> +_supported_os Linux
> +_require_scratch_dax
> +_require_test_program "t_mmap_write_ro"
> +_require_user

Could also maybe benefit from "_require_test", which makes sure your TEST_DEV
is a block device? I don't think you get this explicitly tested with
_test_cycle_mount?

I think you're also missing a:
_require_pmem_key_value $SCRATCH_DEV "mode" "memory"