block/file-*: *_parse_filename() and colons
The file drivers' *_parse_filename() implementations just strip the
optional protocol prefix off the filename. However, for e.g.
"file:foo:bar", this would lead to "foo:bar" being stored as the BDS's
filename which looks like it should be managed using the "foo" protocol.
This is especially troublesome if you then try to resolve a backing
filename based on "foo:bar".
This issue can only occur if the stripped part is a relative filename
("file:/foo:bar" will be shortened to "/foo:bar" and having a slash
before the first colon means that "/foo" is not recognized as a protocol
part). Therefore, we can easily fix it by prepending "./" to such
filenames.
Before this patch:
$ ./qemu-img create -f qcow2 backing.qcow2 64M
Formatting 'backing.qcow2', fmt=qcow2 size=67108864 encryption=off
cluster_size=65536 lazy_refcounts=off refcount_bits=16
$ ./qemu-img create -f qcow2 -b backing.qcow2 file:top:image.qcow2
Formatting 'file:top:image.qcow2', fmt=qcow2 size=67108864
backing_file=backing.qcow2 encryption=off cluster_size=65536
lazy_refcounts=off refcount_bits=16
$ ./qemu-io file:top:image.qcow2
can't open device file:top:image.qcow2: Could not open backing file:
Unknown protocol 'top'
After this patch:
$ ./qemu-io file:top:image.qcow2
[no error]
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170522195217.12991-3-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block.c b/block.c
index b72b872..fa1d06d 100644
--- a/block.c
+++ b/block.c
@@ -197,6 +197,41 @@
}
}
+/*
+ * Helper function for bdrv_parse_filename() implementations to remove optional
+ * protocol prefixes (especially "file:") from a filename and for putting the
+ * stripped filename into the options QDict if there is such a prefix.
+ */
+void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
+ QDict *options)
+{
+ if (strstart(filename, prefix, &filename)) {
+ /* Stripping the explicit protocol prefix may result in a protocol
+ * prefix being (wrongly) detected (if the filename contains a colon) */
+ if (path_has_protocol(filename)) {
+ QString *fat_filename;
+
+ /* This means there is some colon before the first slash; therefore,
+ * this cannot be an absolute path */
+ assert(!path_is_absolute(filename));
+
+ /* And we can thus fix the protocol detection issue by prefixing it
+ * by "./" */
+ fat_filename = qstring_from_str("./");
+ qstring_append(fat_filename, filename);
+
+ assert(!path_has_protocol(qstring_get_str(fat_filename)));
+
+ qdict_put(options, "filename", fat_filename);
+ } else {
+ /* If no protocol prefix was detected, we can use the shortened
+ * filename as-is */
+ qdict_put_str(options, "filename", filename);
+ }
+ }
+}
+
+
/* Returns whether the image file is opened as read-only. Note that this can
* return false and writing to the image file is still not possible because the
* image is inactivated. */
diff --git a/block/file-posix.c b/block/file-posix.c
index 4354d49..de2d3a2 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -381,12 +381,7 @@
static void raw_parse_filename(const char *filename, QDict *options,
Error **errp)
{
- /* The filename does not have to be prefixed by the protocol name, since
- * "file" is the default protocol; therefore, the return value of this
- * function call can be ignored. */
- strstart(filename, "file:", &filename);
-
- qdict_put_str(options, "filename", filename);
+ bdrv_parse_filename_strip_prefix(filename, "file:", options);
}
static QemuOptsList raw_runtime_opts = {
@@ -2395,10 +2390,7 @@
static void hdev_parse_filename(const char *filename, QDict *options,
Error **errp)
{
- /* The prefix is optional, just as for "file". */
- strstart(filename, "host_device:", &filename);
-
- qdict_put_str(options, "filename", filename);
+ bdrv_parse_filename_strip_prefix(filename, "host_device:", options);
}
static bool hdev_is_sg(BlockDriverState *bs)
@@ -2697,10 +2689,7 @@
static void cdrom_parse_filename(const char *filename, QDict *options,
Error **errp)
{
- /* The prefix is optional, just as for "file". */
- strstart(filename, "host_cdrom:", &filename);
-
- qdict_put_str(options, "filename", filename);
+ bdrv_parse_filename_strip_prefix(filename, "host_cdrom:", options);
}
#endif
diff --git a/block/file-win32.c b/block/file-win32.c
index 8f14f0b..ef2910b 100644
--- a/block/file-win32.c
+++ b/block/file-win32.c
@@ -276,12 +276,7 @@
static void raw_parse_filename(const char *filename, QDict *options,
Error **errp)
{
- /* The filename does not have to be prefixed by the protocol name, since
- * "file" is the default protocol; therefore, the return value of this
- * function call can be ignored. */
- strstart(filename, "file:", &filename);
-
- qdict_put_str(options, "filename", filename);
+ bdrv_parse_filename_strip_prefix(filename, "file:", options);
}
static QemuOptsList raw_runtime_opts = {
@@ -671,10 +666,7 @@
static void hdev_parse_filename(const char *filename, QDict *options,
Error **errp)
{
- /* The prefix is optional, just as for "file". */
- strstart(filename, "host_device:", &filename);
-
- qdict_put_str(options, "filename", filename);
+ bdrv_parse_filename_strip_prefix(filename, "host_device:", options);
}
static int hdev_open(BlockDriverState *bs, QDict *options, int flags,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 8d3724c..e5eb473 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -682,6 +682,9 @@
BlockDriver *bdrv_probe_all(const uint8_t *buf, int buf_size,
const char *filename);
+void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
+ QDict *options);
+
/**
* bdrv_add_before_write_notifier:
