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qcow2: Fix NULL dereference in qcow2_open() error path (CVE-2014-0146) 

The qcow2 code assumes that s->snapshots is non-NULL if s->nb_snapshots
!= 0. By having the initialisation of both fields separated in
qcow2_open(), any error occuring in between would cause the error path
to dereference NULL in qcow2_free_snapshots() if the image had any
snapshots.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2014-03-26 13:06:04 +01:00 committed by Stefan Hajnoczi
parent 6b7d4c5558
commit 11b128f406
3 changed files with 15 additions and 3 deletions
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7
block/qcow2.c
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@ -637,9 +637,6 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
goto fail;
}
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
/* read the level 1 table */
if (header.l1_size > 0x2000000) {
/* 32 MB L1 table is enough for 2 PB images at 64k cluster size
@ -734,6 +731,10 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
bs->backing_file[len] = '\0';
}
/* Internal snapshots */
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
ret = qcow2_read_snapshots(bs);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not read snapshots");

7
tests/qemu-iotests/080
View File

@ -138,6 +138,13 @@ poke_file "$TEST_IMG" "$offset_l1_table_offset" "\x12\x34\x56\x78\x90\xab\xcd\xe
poke_file "$TEST_IMG" "$offset_l1_size" "\x00\x00\x00\x01"
{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== Invalid L1 table (with internal snapshot in the image) =="
_make_test_img 64M
{ $QEMU_IMG snapshot -c foo $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
poke_file "$TEST_IMG" "$offset_l1_size" "\x00\x00\x00\x00"
_img_info
echo
echo "== Invalid backing file size =="
_make_test_img 64M

4
tests/qemu-iotests/080.out
View File

@ -59,6 +59,10 @@ no file open, try 'help open'
qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
no file open, try 'help open'
== Invalid L1 table (with internal snapshot in the image) ==
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
qemu-img: Could not open 'TEST_DIR/t.IMGFMT': L1 table is too small
== Invalid backing file size ==
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
qemu-io: can't open device TEST_DIR/t.qcow2: Backing file name too long