qcow2: Fix header extension size check

After reading the extension header, offset is incremented, but not
checked against end_offset any more. This way an integer overflow could
happen when checking whether the extension end is within the allowed
range, effectively disabling the check.

This patch adds the missing check and a test case for it.

Cc: qemu-stable@nongnu.org
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 1416935562-7760-2-git-send-email-kwolf@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 2ebafc854d109ff09b66fb4dd62c2c53fc29754a)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/qcow2.c b/block/qcow2.c
index d53f18182915502925765e5ee12b6d33b7a6c44d..ea6d3f27e187b0023c72cf0333838988a1afb3d4 100644 (file)
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -114,7 +114,7 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
 #ifdef DEBUG_EXT
         printf("ext.magic = 0x%x\n", ext.magic);
 #endif
-        if (ext.len > end_offset - offset) {
+        if (offset > end_offset || ext.len > end_offset - offset) {
             error_setg(errp, "Header extension too large");
             return -EINVAL;
         }

diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080
index 6b3a3e77a5f576d0725f0058eb0980520a5c150c..b9f9630db8c78d043d225e6f21dd67229b889cea 100755 (executable)
--- a/tests/qemu-iotests/080
+++ b/tests/qemu-iotests/080
@@ -78,6 +78,8 @@ poke_file "$TEST_IMG" "$offset_backing_file_offset" "\xff\xff\xff\xff\xff\xff\xf
 poke_file "$TEST_IMG" "$offset_ext_magic" "\x12\x34\x56\x78"
 poke_file "$TEST_IMG" "$offset_ext_size" "\x7f\xff\xff\xff"
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x00\x$(printf %x $offset_ext_size)"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x00\x00"
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 

diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
index f7a943c7a4275f163e6f011da5ad2a4120fe49ea..33d1f71232dfd272837ba5403126e8ef2259504a 100644 (file)
--- a/tests/qemu-iotests/080.out
+++ b/tests/qemu-iotests/080.out
@@ -13,6 +13,8 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Invalid backing file offset
 no file open, try 'help open'
 qemu-io: can't open device TEST_DIR/t.qcow2: Header extension too large
 no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Header extension too large
+no file open, try 'help open'
 
 == Huge refcount table size ==
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864