Commit 46485de0 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

qcow1: Validate image size (CVE-2014-0223) 



A huge image size could cause s->l1_size to overflow. Make sure that
images never require a L1 table larger than what fits in s->l1_size.

This cannot only cause unbounded allocations, but also the allocation of
a too small L1 table, resulting in out-of-bounds array accesses (both
reads and writes).

Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 42eb5817

block/qcow.c

+14 −2
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ typedef struct BDRVQcowState { 
    int cluster_sectors;

    int l2_bits;

    int l2_size;

    int l1_size;

    unsigned int l1_size;

    uint64_t cluster_offset_mask;

    uint64_t l1_table_offset;

    uint64_t *l1_table;
@@ -166,7 +166,19 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags, 


    /* read the level 1 table */

    shift = s->cluster_bits + s->l2_bits;

    s->l1_size = (header.size + (1LL << shift) - 1) >> shift;

    if (header.size > UINT64_MAX - (1LL << shift)) {

        error_setg(errp, "Image too large");

        ret = -EINVAL;

        goto fail;

    } else {

        uint64_t l1_size = (header.size + (1LL << shift) - 1) >> shift;

        if (l1_size > INT_MAX / sizeof(uint64_t)) {

            error_setg(errp, "Image too large");

            ret = -EINVAL;

            goto fail;

        }

        s->l1_size = l1_size;

    }



    s->l1_table_offset = header.l1_table_offset;

    s->l1_table = g_malloc(s->l1_size * sizeof(uint64_t));

tests/qemu-iotests/092

+9 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ _supported_fmt qcow 
_supported_proto generic

_supported_os Linux



offset_size=24

offset_cluster_bits=32

offset_l2_bits=33
@@ -72,6 +73,14 @@ poke_file "$TEST_IMG" "$offset_l2_bits" "\x0e" 
poke_file "$TEST_IMG" "$offset_l2_bits" "\x1b"

{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir



echo

echo "== Invalid size =="

_make_test_img 64M

poke_file "$TEST_IMG" "$offset_size" "\xee\xee\xee\xee\xee\xee\xee\xee"

{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir

poke_file "$TEST_IMG" "$offset_size" "\x7f\xff\xff\xff\xff\xff\xff\xff"

{ $QEMU_IO -c "write 0 64M" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir



# success, all done

echo "*** done"

rm -f $seq.full

tests/qemu-iotests/092.out

+7 −0
Original line number Diff line number Diff line
@@ -21,4 +21,11 @@ qemu-io: can't open device TEST_DIR/t.qcow: L2 table size must be between 512 an 
no file open, try 'help open'

qemu-io: can't open device TEST_DIR/t.qcow: L2 table size must be between 512 and 64k

no file open, try 'help open'



== Invalid size ==

Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 

qemu-io: can't open device TEST_DIR/t.qcow: Image too large

no file open, try 'help open'

qemu-io: can't open device TEST_DIR/t.qcow: Image too large

no file open, try 'help open'

*** done