From 03c320d803fd881736b63015048498cf97d410d3 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Mon, 22 May 2017 21:52:16 +0200 Subject: [PATCH] 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 Message-id: 20170522195217.12991-3-mreitz@redhat.com Reviewed-by: Eric Blake Signed-off-by: Max Reitz --- block.c | 35 +++++++++++++++++++++++++++++++++++ block/file-posix.c | 17 +++-------------- block/file-win32.c | 12 ++---------- include/block/block_int.h | 3 +++ 4 files changed, 43 insertions(+), 24 deletions(-) diff --git a/block.c b/block.c index b72b872806..fa1d06d846 100644 --- a/block.c +++ b/block.c @@ -197,6 +197,41 @@ void path_combine(char *dest, int dest_size, } } +/* + * 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 4354d49642..de2d3a2e3c 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -381,12 +381,7 @@ static void raw_parse_flags(int bdrv_flags, int *open_flags) 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 int check_hdev_writable(BDRVRawState *s) 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 BlockDriver bdrv_host_device = { 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 8f14f0bdcd..ef2910b03f 100644 --- a/block/file-win32.c +++ b/block/file-win32.c @@ -276,12 +276,7 @@ static void raw_parse_flags(int flags, bool use_aio, int *access_flags, 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 int hdev_probe_device(const char *filename) 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 8d3724cce6..e5eb473e53 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -682,6 +682,9 @@ int get_tmp_filename(char *filename, int size); 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: -- 2.11.4.GIT