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block: Raise an error when backing file parameter is an empty string

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Providing an empty string for the backing file parameter like so:

	qemu-img create -f qcow2 -b '' /tmp/foo

allows the flow of control to reach and subsequently fail an assert
statement because passing an empty string to

	bdrv_get_full_backing_filename_from_filename()

simply results in NULL being returned without an error being raised.

To fix this, let's check for an empty string when getting the value from
the opts list.

Reported-by: Attila Fazekas <afazekas@redhat.com>
Fixes: https://bugzilla.redhat.com/1809553
Signed-off-by: Connor Kuehl <ckuehl@redhat.com>
Message-Id: <20200813134722.802180-1-ckuehl@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Connor Kuehl 2020-08-13 08:47:22 -05:00 committed by Kevin Wolf
parent 7c37270b3f
commit 975a7bd228
3 changed files with 13 additions and 0 deletions
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4
block.c
View file

@ -6119,6 +6119,10 @@ void bdrv_img_create(const char *filename, const char *fmt,
"same filename as the backing file");
goto out;
}
if (backing_file[0] == '\0') {
error_setg(errp, "Expected backing file name, got empty string");
goto out;
}
}
backing_fmt = qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT);

4
tests/qemu-iotests/049
View file

@ -119,6 +119,10 @@ test_qemu_img create -f $IMGFMT -o compat=1.1,lazy_refcounts=on "$TEST_IMG" 64M
test_qemu_img create -f $IMGFMT -o compat=0.10,lazy_refcounts=off "$TEST_IMG" 64M
test_qemu_img create -f $IMGFMT -o compat=0.10,lazy_refcounts=on "$TEST_IMG" 64M
echo "== Expect error when backing file name is empty string =="
echo
test_qemu_img create -f $IMGFMT -b '' $TEST_IMG 1M
# success, all done
echo "*** done"
rm -f $seq.full

5
tests/qemu-iotests/049.out
View file

@ -209,4 +209,9 @@ qemu-img create -f qcow2 -o compat=0.10,lazy_refcounts=on TEST_DIR/t.qcow2 64M
Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=67108864 compat=0.10 lazy_refcounts=on refcount_bits=16
qemu-img: TEST_DIR/t.qcow2: Lazy refcounts only supported with compatibility level 1.1 and above (use version=v3 or greater)
== Expect error when backing file name is empty string ==
qemu-img create -f qcow2 -b TEST_DIR/t.qcow2 1M
qemu-img: TEST_DIR/t.qcow2: Expected backing file name, got empty string
*** done