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From 38b7ffbe3a1fa62f4d5177a3a572aa1c9abb1963 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Tue, 25 Mar 2014 14:23:33 +0100
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Subject: [PATCH 26/49] qcow2: Fix backing file name length check
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <1395753835-7591-27-git-send-email-kwolf@redhat.com>
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Patchwork-id: n/a
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O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 26/48] qcow2: Fix backing file name length check
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Bugzilla: 1066691
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RH-Acked-by: Jeff Cody <jcody@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1066691
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Upstream status: Series embargoed
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len could become negative and would pass the check then. Nothing bad
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happened because bdrv_pread() happens to return an error for negative
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length values, but make variables for sizes unsigned anyway.
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This patch also changes the behaviour to error out on invalid lengths
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instead of silently truncating it to 1023.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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block/qcow2.c | 9 ++++++---
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tests/qemu-iotests/080 | 8 ++++++++
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tests/qemu-iotests/080.out | 5 +++++
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3 files changed, 19 insertions(+), 3 deletions(-)
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diff --git a/block/qcow2.c b/block/qcow2.c
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index 8be82f0..a8ad9e1 100644
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--- a/block/qcow2.c
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+++ b/block/qcow2.c
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@@ -445,7 +445,8 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
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Error **errp)
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{
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BDRVQcowState *s = bs->opaque;
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- int len, i, ret = 0;
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+ unsigned int len, i;
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+ int ret = 0;
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QCowHeader header;
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QemuOpts *opts;
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Error *local_err = NULL;
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@@ -720,8 +721,10 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
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/* read the backing file name */
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if (header.backing_file_offset != 0) {
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len = header.backing_file_size;
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- if (len > 1023) {
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- len = 1023;
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+ if (len > MIN(1023, s->cluster_size - header.backing_file_offset)) {
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+ error_setg(errp, "Backing file name too long");
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+ ret = -EINVAL;
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+ goto fail;
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}
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ret = bdrv_pread(bs->file, header.backing_file_offset,
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bs->backing_file, len);
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diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080
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index 7255b6c..f3091a9 100755
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--- a/tests/qemu-iotests/080
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+++ b/tests/qemu-iotests/080
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@@ -45,6 +45,7 @@ _supported_os Linux
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header_size=104
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offset_backing_file_offset=8
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+offset_backing_file_size=16
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offset_l1_size=36
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offset_l1_table_offset=40
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offset_refcount_table_offset=48
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@@ -135,6 +136,13 @@ poke_file "$TEST_IMG" "$offset_l1_table_offset" "\x12\x34\x56\x78\x90\xab\xcd\xe
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poke_file "$TEST_IMG" "$offset_l1_size" "\x00\x00\x00\x01"
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{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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+echo
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+echo "== Invalid backing file size =="
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+_make_test_img 64M
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+poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x10\x00"
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+poke_file "$TEST_IMG" "$offset_backing_file_size" "\xff\xff\xff\xff"
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+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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+
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# success, all done
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echo "*** done"
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rm -f $seq.full
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diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
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index 4ec2545..8103211 100644
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--- a/tests/qemu-iotests/080.out
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+++ b/tests/qemu-iotests/080.out
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@@ -58,4 +58,9 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
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no file open, try 'help open'
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qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
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no file open, try 'help open'
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+
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+== Invalid backing file size ==
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+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
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+qemu-io: can't open device TEST_DIR/t.qcow2: Backing file name too long
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+no file open, try 'help open'
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*** done
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--
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1.7.1
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