From c2e857b4cac0186d4ba1521fcfeb9b5322831676 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Mon, 8 Apr 2024 15:38:11 +0200 Subject: [PATCH] hw/sd/sdcard: Avoid OOB in sd_read_byte() during unexpected CMD switch MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit For multi-bytes commands, our implementation uses the @data_start and @data_offset fields to track byte access. We initialize the command start/offset in buffer once. Malicious guest might abuse by switching command while staying in the 'transfer' state, switching command buffer size, and our implementation can access out of buffer boundary. For example, CMD17 (READ_SINGLE_BLOCK) allows to read up to 512 bytes, and CMD13 (SEND_STATUS) up to 64 bytes. By switching from CMD17 to CMD13 (see reproducer below), bytes [64-511] are out of the 'status' buffer. Our implementation return R0 status code for unexpected commands. Such in-transaction command switch is unexpected and returns R0. This is a good place to reset the start/offset fields to avoid malicious accesses. Can be reproduced running: $ export UBSAN_OPTIONS=print_stacktrace=1:halt_on_error=1 $ cat << EOF | qemu-system-i386 \ -display none -nographic \ -machine accel=qtest -m 512M \ -nodefaults \ -device sdhci-pci,sd-spec-version=3 \ -device sd-card,drive=mydrive \ -drive if=none,index=0,file=null-co://,format=raw,id=mydrive \ -qtest stdio -trace sd\* -trace -sdbus_read outl 0xcf8 0x80001010 outl 0xcfc 0xe0000000 outl 0xcf8 0x80001004 outw 0xcfc 0x02 write 0xe000002c 0x1 0x05 write 0xe000000f 0x1 0x37 write 0xe000000a 0x1 0x01 write 0xe000000f 0x1 0x29 write 0xe000000f 0x1 0x02 write 0xe000000f 0x1 0x03 write 0xe000000c 0x1 0x32 write 0xe000000f 0x1 0x06 write 0xe0000005 0x1 0x01 write 0xe0000007 0x1 0x01 write 0xe0000003 0x1 0x00 write 0xe000000f 0x1 0x11 write 0xe000002a 0x1 0x01 write 0xe000002a 0x1 0x02 write 0xe000000f 0x1 0x0d write 0xe000002a 0x1 0x01 write 0xe000002a 0x1 0x02 EOF hw/sd/sd.c:1984:15: runtime error: index 256 out of bounds for type 'uint8_t [64]' #0 sd_read_byte hw/sd/sd.c:1984:15 #1 sdbus_read_data hw/sd/core.c:157:23 #2 sdhci_read_block_from_card hw/sd/sdhci.c:423:9 #3 sdhci_blkgap_write hw/sd/sdhci.c:1074:13 #4 sdhci_write hw/sd/sdhci.c:1195:13 #5 memory_region_write_accessor softmmu/memory.c:492:5 #6 access_with_adjusted_size softmmu/memory.c:554:18 #7 memory_region_dispatch_write softmmu/memory.c #8 flatview_write_continue softmmu/physmem.c:2778:23 #9 flatview_write softmmu/physmem.c:2818:14 #10 address_space_write softmmu/physmem.c:2910:18 SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior hw/sd/sd.c:1984:15 Reported-by: Alexander Bulekov Resolves: https://gitlab.com/qemu-project/qemu/-/issues/487 Buglink: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36240 Signed-off-by: Philippe Mathieu-Daudé Message-Id: <20240408141717.66154-2-philmd@linaro.org> --- hw/sd/sd.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/hw/sd/sd.c b/hw/sd/sd.c index 807b5d3de32..6a7a10501bd 100644 --- a/hw/sd/sd.c +++ b/hw/sd/sd.c @@ -1826,6 +1826,13 @@ int sd_do_command(SDState *sd, SDRequest *req, break; case sd_r0: + /* + * Invalid state transition, reset implementation + * fields to avoid OOB abuse. + */ + sd->data_start = 0; + sd->data_offset = 0; + /* fall-through */ case sd_illegal: rsplen = 0; break;