From 6d33e8e7dc9d40ea105feed4b39caa3e641569e8 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 26 Mar 2014 13:05:47 +0100 Subject: [PATCH] qcow2: Fix backing file name length check len could become negative and would pass the check then. Nothing bad happened because bdrv_pread() happens to return an error for negative length values, but make variables for sizes unsigned anyway. This patch also changes the behaviour to error out on invalid lengths instead of silently truncating it to 1023. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Signed-off-by: Stefan Hajnoczi --- block/qcow2.c | 9 ++++++--- tests/qemu-iotests/080 | 8 ++++++++ tests/qemu-iotests/080.out | 5 +++++ 3 files changed, 19 insertions(+), 3 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 36395289a9..cc1bfebf29 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -445,7 +445,8 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { BDRVQcowState *s = bs->opaque; - int len, i, ret = 0; + unsigned int len, i; + int ret = 0; QCowHeader header; QemuOpts *opts; Error *local_err = NULL; @@ -721,8 +722,10 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, /* read the backing file name */ if (header.backing_file_offset != 0) { len = header.backing_file_size; - if (len > 1023) { - len = 1023; + if (len > MIN(1023, s->cluster_size - header.backing_file_offset)) { + error_setg(errp, "Backing file name too long"); + ret = -EINVAL; + goto fail; } ret = bdrv_pread(bs->file, header.backing_file_offset, bs->backing_file, len); diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080 index 7255b6cca6..f3091a9377 100755 --- a/tests/qemu-iotests/080 +++ b/tests/qemu-iotests/080 @@ -45,6 +45,7 @@ _supported_os Linux header_size=104 offset_backing_file_offset=8 +offset_backing_file_size=16 offset_l1_size=36 offset_l1_table_offset=40 offset_refcount_table_offset=48 @@ -135,6 +136,13 @@ 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" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir +echo +echo "== Invalid backing file size ==" +_make_test_img 64M +poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x10\x00" +poke_file "$TEST_IMG" "$offset_backing_file_size" "\xff\xff\xff\xff" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir + # success, all done echo "*** done" rm -f $seq.full diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out index 4ec2545051..8103211064 100644 --- a/tests/qemu-iotests/080.out +++ b/tests/qemu-iotests/080.out @@ -58,4 +58,9 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset 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 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 +no file open, try 'help open' *** done