From 6eff47e72cb2f23d168be58bab8bdd60df49afd0 Mon Sep 17 00:00:00 2001 From: Christophe Fergeau Date: Thu, 29 Nov 2018 14:18:39 +0100 Subject: [spice-server] memslot: Fix off-by-one error in group/slot boundary check RedMemSlotInfo keeps an array of groups, and each group contains an array of slots. Unfortunately, these checks are off by 1, they check that the index is greater or equal to the number of elements in the array, while these arrays are 0 based. The check should only check for strictly greater than the number of elements. For the group array, this is not a big issue, as these memslot groups are created by spice-server users (eg QEMU), and the group ids used to index that array are also generated by the spice-server user, so it should not be possible for the guest to set them to arbitrary values. The slot id is more problematic, as it's calculated from a QXLPHYSICAL address, and such addresses are usually set by the guest QXL driver, so the guest can set these to arbitrary values, including malicious values, which are probably easy to build from the guest PCI configuration. This patch fixes the arrays bound check, and adds a test case for this. Signed-off-by: Christophe Fergeau --- server/memslot.c | 4 ++-- server/tests/test-qxl-parsing.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+), 2 deletions(-) diff --git a/server/memslot.c b/server/memslot.c index b27324efb..fb3d5cfd5 100644 --- a/server/memslot.c +++ b/server/memslot.c @@ -97,13 +97,13 @@ void *memslot_get_virt(RedMemSlotInfo *info, QXLPHYSICAL addr, uint32_t add_size MemSlot *slot; - if (group_id > info->num_memslots_groups) { + if (group_id >= info->num_memslots_groups) { g_critical("group_id too big"); return NULL; } slot_id = memslot_get_id(info, addr); - if (slot_id > info->num_memslots) { + if (slot_id >= info->num_memslots) { print_memslots(info); g_critical("slot_id %d too big, addr=%" PRIx64, slot_id, addr); return NULL; diff --git a/server/tests/test-qxl-parsing.c b/server/tests/test-qxl-parsing.c index 8565239f0..447425984 100644 --- a/server/tests/test-qxl-parsing.c +++ b/server/tests/test-qxl-parsing.c @@ -98,6 +98,31 @@ static void deinit_qxl_surface(QXLSurfaceCmd *qxl) g_free(from_physical(qxl->u.surface_create.data)); } +static void test_memslot_invalid_group_id(void) +{ + RedMemSlotInfo mem_info; + init_meminfo(&mem_info); + + memslot_get_virt(&mem_info, 0, 16, 1); +} + +static void test_memslot_invalid_slot_id(void) +{ + RedMemSlotInfo mem_info; + init_meminfo(&mem_info); + + memslot_get_virt(&mem_info, 1 << mem_info.memslot_id_shift, 16, 0); +} + +static void test_memslot_invalid_addresses(void) +{ + g_test_trap_subprocess("/server/memslot-invalid-addresses/subprocess/group_id", 0, 0); + g_test_trap_assert_stderr("*group_id too big*"); + + g_test_trap_subprocess("/server/memslot-invalid-addresses/subprocess/slot_id", 0, 0); + g_test_trap_assert_stderr("*slot_id 1 too big*"); +} + static void test_no_issues(void) { RedMemSlotInfo mem_info; @@ -317,6 +342,11 @@ int main(int argc, char *argv[]) { g_test_init(&argc, &argv, NULL); + /* try to use invalid memslot group/slot */ + g_test_add_func("/server/memslot-invalid-addresses", test_memslot_invalid_addresses); + g_test_add_func("/server/memslot-invalid-addresses/subprocess/group_id", test_memslot_invalid_group_id); + g_test_add_func("/server/memslot-invalid-addresses/subprocess/slot_id", test_memslot_invalid_slot_id); + /* try to create a surface with no issues, should succeed */ g_test_add_func("/server/qxl-parsing-no-issues", test_no_issues); -- 2.19.2