From 0b7385ddaa538c5995d2f16333a80a0f579a6212 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 25 Mar 2014 14:23:46 +0100 Subject: [PATCH 39/49] dmg: prevent chunk buffer overflow (CVE-2014-0145) RH-Author: Kevin Wolf Message-id: <1395753835-7591-40-git-send-email-kwolf@redhat.com> Patchwork-id: n/a O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 39/48] dmg: prevent chunk buffer overflow (CVE-2014-0145) Bugzilla: 1079325 RH-Acked-by: Jeff Cody RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Paolo Bonzini From: Stefan Hajnoczi Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1079325 Upstream status: Embargoed Both compressed and uncompressed I/O is buffered. dmg_open() calculates the maximum buffer size needed from the metadata in the image file. There is currently a buffer overflow since ->lengths[] is accounted against the maximum compressed buffer size but actually uses the uncompressed buffer: switch (s->types[chunk]) { 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/ ret = bdrv_pread(bs->file, s->offsets[chunk], s->uncompressed_chunk, s->lengths[chunk]); We must account against the maximum uncompressed buffer size for type=1 chunks. This patch fixes the maximum buffer size calculation to take into account the chunk type. It is critical that we update the correct maximum since there are two buffers ->compressed_chunk and ->uncompressed_chunk. Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/dmg.c | 39 +++++++++++++++++++++++++++++++++------ 1 files changed, 33 insertions(+), 6 deletions(-) diff --git a/block/dmg.c b/block/dmg.c index be0ee33..856402e 100644 --- a/block/dmg.c +++ b/block/dmg.c @@ -100,6 +100,37 @@ static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result) return 0; } +/* Increase max chunk sizes, if necessary. This function is used to calculate + * the buffer sizes needed for compressed/uncompressed chunk I/O. + */ +static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk, + uint32_t *max_compressed_size, + uint32_t *max_sectors_per_chunk) +{ + uint32_t compressed_size = 0; + uint32_t uncompressed_sectors = 0; + + switch (s->types[chunk]) { + case 0x80000005: /* zlib compressed */ + compressed_size = s->lengths[chunk]; + uncompressed_sectors = s->sectorcounts[chunk]; + break; + case 1: /* copy */ + uncompressed_sectors = (s->lengths[chunk] + 511) / 512; + break; + case 2: /* zero */ + uncompressed_sectors = s->sectorcounts[chunk]; + break; + } + + if (compressed_size > *max_compressed_size) { + *max_compressed_size = compressed_size; + } + if (uncompressed_sectors > *max_sectors_per_chunk) { + *max_sectors_per_chunk = uncompressed_sectors; + } +} + static int dmg_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { @@ -245,12 +276,8 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } - if (s->lengths[i] > max_compressed_size) { - max_compressed_size = s->lengths[i]; - } - if (s->sectorcounts[i] > max_sectors_per_chunk) { - max_sectors_per_chunk = s->sectorcounts[i]; - } + update_max_chunk_size(s, i, &max_compressed_size, + &max_sectors_per_chunk); } s->n_chunks += chunk_count; } -- 1.7.1