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From 0b7385ddaa538c5995d2f16333a80a0f579a6212 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 25 Mar 2014 14:23:46 +0100
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Subject: [PATCH 39/49] dmg: prevent chunk buffer overflow (CVE-2014-0145)
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <1395753835-7591-40-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 39/48] dmg: prevent chunk buffer overflow (CVE-2014-0145)
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Bugzilla: 1079325
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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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From: Stefan Hajnoczi <stefanha@redhat.com>
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1079325
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Upstream status: Embargoed
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Both compressed and uncompressed I/O is buffered. dmg_open() calculates
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the maximum buffer size needed from the metadata in the image file.
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There is currently a buffer overflow since ->lengths[] is accounted
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against the maximum compressed buffer size but actually uses the
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uncompressed buffer:
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switch (s->types[chunk]) {
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case 1: /bin /boot /cgroup /dev /etc /home /lib /lib64 /lost+found /media /misc /mnt /net /opt /proc /root /sbin /selinux /srv /sys /tmp /usr /var copy audio/ backends/ block/ bsd-user/ default-configs/ disas/ docs/ dtc/ fpu/ fsdev/ gdb-xml/ hw/ include/ ldscripts/ libcacard/ linux-headers/ linux-user/ net/ pc-bios/ pixman/ po/ qapi/ qga/ QMP/ qobject/ qom/ redhat/ roms/ scripts/ slirp/ stubs/ sysconfigs/ target-alpha/ target-arm/ target-cris/ target-i386/ target-lm32/ target-m68k/ target-microblaze/ target-mips/ target-moxie/ target-openrisc/ target-ppc/ target-s390x/ target-sh4/ target-sparc/ target-unicore32/ target-xtensa/ tcg/ tests/ trace/ ui/ util/
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ret = bdrv_pread(bs->file, s->offsets[chunk],
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s->uncompressed_chunk, s->lengths[chunk]);
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We must account against the maximum uncompressed buffer size for type=1
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chunks.
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This patch fixes the maximum buffer size calculation to take into
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account the chunk type. It is critical that we update the correct
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maximum since there are two buffers ->compressed_chunk and
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->uncompressed_chunk.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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block/dmg.c | 39 +++++++++++++++++++++++++++++++++------
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1 files changed, 33 insertions(+), 6 deletions(-)
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diff --git a/block/dmg.c b/block/dmg.c
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index be0ee33..856402e 100644
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--- a/block/dmg.c
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+++ b/block/dmg.c
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@@ -100,6 +100,37 @@ static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
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return 0;
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}
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+/* Increase max chunk sizes, if necessary. This function is used to calculate
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+ * the buffer sizes needed for compressed/uncompressed chunk I/O.
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+ */
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+static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
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+ uint32_t *max_compressed_size,
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+ uint32_t *max_sectors_per_chunk)
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+{
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+ uint32_t compressed_size = 0;
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+ uint32_t uncompressed_sectors = 0;
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+
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+ switch (s->types[chunk]) {
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+ case 0x80000005: /* zlib compressed */
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+ compressed_size = s->lengths[chunk];
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+ uncompressed_sectors = s->sectorcounts[chunk];
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+ break;
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+ case 1: /* copy */
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+ uncompressed_sectors = (s->lengths[chunk] + 511) / 512;
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+ break;
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+ case 2: /* zero */
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+ uncompressed_sectors = s->sectorcounts[chunk];
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+ break;
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+ }
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+
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+ if (compressed_size > *max_compressed_size) {
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+ *max_compressed_size = compressed_size;
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+ }
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+ if (uncompressed_sectors > *max_sectors_per_chunk) {
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+ *max_sectors_per_chunk = uncompressed_sectors;
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+ }
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+}
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+
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static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
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Error **errp)
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{
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@@ -245,12 +276,8 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
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goto fail;
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}
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- if (s->lengths[i] > max_compressed_size) {
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- max_compressed_size = s->lengths[i];
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- }
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- if (s->sectorcounts[i] > max_sectors_per_chunk) {
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- max_sectors_per_chunk = s->sectorcounts[i];
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- }
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+ update_max_chunk_size(s, i, &max_compressed_size,
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+ &max_sectors_per_chunk);
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}
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s->n_chunks += chunk_count;
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}
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--
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1.7.1
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