Hugh notes: "I think that is more restrictive than you intended: haven't tried, but I believe it rejects a PROT_READ, MAP_SHARED, O_RDONLY fd mmap, leaving no way to mmap /dev/dax without write permission to it." Reported-by: Hugh Dickins <hughd(a)google.com&gt; Signed-off-by: Dan Williams <dan.j.williams(a)intel.com&gt; --- test/device-dax.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/test/device-dax.c b/test/device-dax.c index 82154d5c1fff..75b17ed63088 100644 --- a/test/device-dax.c +++ b/test/device-dax.c @@ -201,22 +201,22 @@ static int test_device_dax(int loglevel, struct ndctl_test *test, } sprintf(path, "/dev/%s", daxctl_dev_get_devname(dev)); - fd = open(path, O_RDWR); + fd = open(path, O_RDONLY); if (fd < 0) { - fprintf(stderr, "%s: failed to open device-dax instance\n", + fprintf(stderr, "%s: failed to open(O_RDONLY) device-dax instance\n", daxctl_dev_get_devname(dev)); rc = -ENXIO; goto out; } - buf = mmap(NULL, VERIFY_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0); + buf = mmap(NULL, VERIFY_SIZE, PROT_READ, MAP_PRIVATE, fd, 0); if (buf != MAP_FAILED) { fprintf(stderr, "%s: expected MAP_PRIVATE failure\n", path); rc = -ENXIO; goto out; } - buf = mmap(NULL, VERIFY_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); + buf = mmap(NULL, VERIFY_SIZE, PROT_READ, MAP_SHARED, fd, 0); if (buf == MAP_FAILED) { fprintf(stderr, "%s: expected MAP_SHARED success\n", path); return -ENXIO; @@ -226,6 +226,24 @@ static int test_device_dax(int loglevel, struct ndctl_test *test, if (rc) goto out; + /* upgrade to a writable mapping */ + close(fd); + munmap(buf, VERIFY_SIZE); + fd = open(path, O_RDWR); + if (fd < 0) { + fprintf(stderr, "%s: failed to open(O_RDWR) device-dax instance\n", + daxctl_dev_get_devname(dev)); + rc = -ENXIO; + goto out; + } + + buf = mmap(NULL, VERIFY_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); + if (buf == MAP_FAILED) { + fprintf(stderr, "%s: expected PROT_WRITE + MAP_SHARED success\n", + path); + return -ENXIO; + } + /* * Prior to 4.8-final these tests cause crashes, or are * otherwise not supported.