From bd385a5298d7062668e804d73944d52aec9549f1 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 11 Apr 2024 15:06:01 +0200 Subject: qcow2: Don't open data_file with BDRV_O_NO_IO One use case for 'qemu-img info' is verifying that untrusted images don't reference an unwanted external file, be it as a backing file or an external data file. To make sure that calling 'qemu-img info' can't already have undesired side effects with a malicious image, just don't open the data file at all with BDRV_O_NO_IO. If nothing ever tries to do I/O, we don't need to have it open. This changes the output of iotests case 061, which used 'qemu-img info' to show that opening an image with an invalid data file fails. After this patch, it succeeds. Replace this part of the test with a qemu-io call, but keep the final 'qemu-img info' to show that the invalid data file is correctly displayed in the output. Fixes: CVE-2024-4467 Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek --- block/qcow2.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/qcow2.c b/block/qcow2.c index 10883a2494..70b19730a3 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1636,7 +1636,22 @@ qcow2_do_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } - if (open_data_file) { + if (open_data_file && (flags & BDRV_O_NO_IO)) { + /* + * Don't open the data file for 'qemu-img info' so that it can be used + * to verify that an untrusted qcow2 image doesn't refer to external + * files. + * + * Note: This still makes has_data_file() return true. + */ + if (s->incompatible_features & QCOW2_INCOMPAT_DATA_FILE) { + s->data_file = NULL; + } else { + s->data_file = bs->file; + } + qdict_extract_subqdict(options, NULL, "data-file."); + qdict_del(options, "data-file"); + } else if (open_data_file) { /* Open external data file */ bdrv_graph_co_rdunlock(); s->data_file = bdrv_co_open_child(NULL, options, "data-file", bs, -- cgit v1.2.3