From 2318681bf850996a3e9c682ca3290aa9f05fd15c Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 25 Mar 2014 14:23:31 +0100 Subject: [PATCH 24/49] qcow2: Validate snapshot table offset/size (CVE-2014-0144) RH-Author: Kevin Wolf Message-id: <1395753835-7591-25-git-send-email-kwolf@redhat.com> Patchwork-id: n/a O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 24/48] qcow2: Validate snapshot table offset/size (CVE-2014-0144) Bugzilla: 1079455 RH-Acked-by: Jeff Cody RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Paolo Bonzini Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1079455 Upstream status: Embargoed This avoid unbounded memory allocation and fixes a potential buffer overflow on 32 bit hosts. Signed-off-by: Kevin Wolf --- block/qcow2-snapshot.c | 29 ++++------------------------- block/qcow2.c | 15 +++++++++++++++ block/qcow2.h | 29 ++++++++++++++++++++++++++++- tests/qemu-iotests/080 | 27 +++++++++++++++++++++++++++ tests/qemu-iotests/080.out | 17 +++++++++++++++++ 5 files changed, 91 insertions(+), 26 deletions(-) diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c index aa88c51..5d73506 100644 --- a/block/qcow2-snapshot.c +++ b/block/qcow2-snapshot.c @@ -26,31 +26,6 @@ #include "block/block_int.h" #include "block/qcow2.h" -typedef struct QEMU_PACKED QCowSnapshotHeader { - /* header is 8 byte aligned */ - uint64_t l1_table_offset; - - uint32_t l1_size; - uint16_t id_str_size; - uint16_t name_size; - - uint32_t date_sec; - uint32_t date_nsec; - - uint64_t vm_clock_nsec; - - uint32_t vm_state_size; - uint32_t extra_data_size; /* for extension */ - /* extra data follows */ - /* id_str follows */ - /* name follows */ -} QCowSnapshotHeader; - -typedef struct QEMU_PACKED QCowSnapshotExtraData { - uint64_t vm_state_size_large; - uint64_t disk_size; -} QCowSnapshotExtraData; - void qcow2_free_snapshots(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; @@ -334,6 +309,10 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info) uint64_t *l1_table = NULL; int64_t l1_table_offset; + if (s->nb_snapshots >= QCOW_MAX_SNAPSHOTS) { + return -EFBIG; + } + memset(sn, 0, sizeof(*sn)); /* Generate an ID if it wasn't passed */ diff --git a/block/qcow2.c b/block/qcow2.c index 5513fac..8c74dea 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -622,6 +622,21 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } + /* Snapshot table offset/length */ + if (header.nb_snapshots > QCOW_MAX_SNAPSHOTS) { + error_setg(errp, "Too many snapshots"); + ret = -EINVAL; + goto fail; + } + + ret = validate_table_offset(bs, header.snapshots_offset, + header.nb_snapshots, + sizeof(QCowSnapshotHeader)); + if (ret < 0) { + error_setg(errp, "Invalid snapshot table offset"); + goto fail; + } + s->snapshots_offset = header.snapshots_offset; s->nb_snapshots = header.nb_snapshots; diff --git a/block/qcow2.h b/block/qcow2.h index 4a653c5..5efc96e 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -38,6 +38,7 @@ #define QCOW_CRYPT_AES 1 #define QCOW_MAX_CRYPT_CLUSTERS 32 +#define QCOW_MAX_SNAPSHOTS 65536 /* indicate that the refcount of the referenced cluster is exactly one. */ #define QCOW_OFLAG_COPIED (1LL << 63) @@ -97,6 +98,32 @@ typedef struct QCowHeader { uint32_t header_length; } QCowHeader; +typedef struct QEMU_PACKED QCowSnapshotHeader { + /* header is 8 byte aligned */ + uint64_t l1_table_offset; + + uint32_t l1_size; + uint16_t id_str_size; + uint16_t name_size; + + uint32_t date_sec; + uint32_t date_nsec; + + uint64_t vm_clock_nsec; + + uint32_t vm_state_size; + uint32_t extra_data_size; /* for extension */ + /* extra data follows */ + /* id_str follows */ + /* name follows */ +} QCowSnapshotHeader; + +typedef struct QEMU_PACKED QCowSnapshotExtraData { + uint64_t vm_state_size_large; + uint64_t disk_size; +} QCowSnapshotExtraData; + + typedef struct QCowSnapshot { uint64_t l1_table_offset; uint32_t l1_size; @@ -202,7 +229,7 @@ typedef struct BDRVQcowState { AES_KEY aes_decrypt_key; uint64_t snapshots_offset; int snapshots_size; - int nb_snapshots; + unsigned int nb_snapshots; QCowSnapshot *snapshots; int flags; diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080 index f58ac73..8a8b460 100755 --- a/tests/qemu-iotests/080 +++ b/tests/qemu-iotests/080 @@ -47,6 +47,8 @@ header_size=104 offset_backing_file_offset=8 offset_refcount_table_offset=48 offset_refcount_table_clusters=56 +offset_nb_snapshots=60 +offset_snapshots_offset=64 offset_header_size=100 offset_ext_magic=$header_size offset_ext_size=$((header_size + 4)) @@ -90,6 +92,31 @@ poke_file "$TEST_IMG" "$offset_refcount_table_offset" "\xff\xff\xff\xff\xff\xff\ poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\x00\x00\x00\x7f" { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir +echo +echo "== Invalid snapshot table ==" +_make_test_img 64M +poke_file "$TEST_IMG" "$offset_nb_snapshots" "\xff\xff\xff\xff" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir +poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x7f\xff\xff\xff" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir + +poke_file "$TEST_IMG" "$offset_snapshots_offset" "\xff\xff\xff\xff\xff\xff\x00\x00" +poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x00\xff\xff" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir + +poke_file "$TEST_IMG" "$offset_snapshots_offset" "\x12\x34\x56\x78\x90\xab\xcd\xef" +poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x00\x00\x00" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir + +echo +echo "== Hitting snapshot table size limit ==" +_make_test_img 64M +# Put the refcount table in a more or less safe place (16 MB) +poke_file "$TEST_IMG" "$offset_snapshots_offset" "\x00\x00\x00\x00\x01\x00\x00\x00" +poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x01\x00\x00" +{ $QEMU_IMG snapshot -c test $TEST_IMG; } 2>&1 | _filter_testdir +{ $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 f919b58..b06f47f 100644 --- a/tests/qemu-iotests/080.out +++ b/tests/qemu-iotests/080.out @@ -30,4 +30,21 @@ no file open, try 'help open' Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 qemu-io: can't open device TEST_DIR/t.qcow2: Invalid reference count table offset no file open, try 'help open' + +== Invalid snapshot table == +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 +qemu-io: can't open device TEST_DIR/t.qcow2: Too many snapshots +no file open, try 'help open' +qemu-io: can't open device TEST_DIR/t.qcow2: Too many snapshots +no file open, try 'help open' +qemu-io: can't open device TEST_DIR/t.qcow2: Invalid snapshot table offset +no file open, try 'help open' +qemu-io: can't open device TEST_DIR/t.qcow2: Invalid snapshot table offset +no file open, try 'help open' + +== Hitting snapshot table size limit == +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 +qemu-img: Could not create snapshot 'test': -27 (File too large) +read 512/512 bytes at offset 0 +512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) *** done -- 1.7.1