From 2ebafc854d109ff09b66fb4dd62c2c53fc29754a Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 25 Nov 2014 18:12:40 +0100 Subject: [PATCH] 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 Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Message-id: 1416935562-7760-2-git-send-email-kwolf@redhat.com Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/qcow2.c | 2 +- tests/qemu-iotests/080 | 2 ++ tests/qemu-iotests/080.out | 2 ++ 3 files changed, 5 insertions(+), 1 deletion(-) diff --git a/block/qcow2.c b/block/qcow2.c index d120494..8b9ffc4 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -117,7 +117,7 @@ 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 9de337c..73795f1 100755 --- 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 f7a943c..33d1f71 100644 --- 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 -- 2.7.4