From 5e73953a276106f8e2be475cca3299748bfd1201 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 10 Nov 2020 22:52:47 +0100 Subject: [PATCH] hw/net/can/ctucan: Don't allow guest to write off end of tx_buffer The ctucan device has 4 CAN bus cores, each of which has a set of 20 32-bit registers for writing the transmitted data. The registers are however not contiguous; each core's buffers is 0x100 bytes after the last. We got the checks on the address wrong in the ctucan_mem_write() function: * the first "is addr in range at all" check allowed addr == CTUCAN_CORE_MEM_SIZE, which is actually the first byte off the end of the range * the decode of addresses into core-number plus offset in the tx buffer for that core failed to check that the offset was in range, so the guest could write off the end of the tx_buffer[] array NB: currently the values of CTUCAN_CORE_MEM_SIZE, CTUCAN_CORE_TXBUF_NUM, etc, make "buff_num >= CTUCAN_CORE_TXBUF_NUM" impossible, but we retain this as a runtime check rather than an assertion to permit those values to be changed in future (in hardware they are configurable synthesis parameters). Fix the top level check, and check the offset is within the buffer. Fixes: Coverity CID 1432874 Signed-off-by: Peter Maydell Signed-off-by: Pavel Pisa Tested-by: Pavel Pisa Signed-off-by: Jason Wang --- hw/net/can/ctucan_core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/hw/net/can/ctucan_core.c b/hw/net/can/ctucan_core.c index d20835cd7e..8486f429d7 100644 --- a/hw/net/can/ctucan_core.c +++ b/hw/net/can/ctucan_core.c @@ -303,7 +303,7 @@ void ctucan_mem_write(CtuCanCoreState *s, hwaddr addr, uint64_t val, DPRINTF("write 0x%02llx addr 0x%02x\n", (unsigned long long)val, (unsigned int)addr); - if (addr > CTUCAN_CORE_MEM_SIZE) { + if (addr >= CTUCAN_CORE_MEM_SIZE) { return; } @@ -312,7 +312,9 @@ void ctucan_mem_write(CtuCanCoreState *s, hwaddr addr, uint64_t val, addr -= CTU_CAN_FD_TXTB1_DATA_1; buff_num = addr / CTUCAN_CORE_TXBUFF_SPAN; addr %= CTUCAN_CORE_TXBUFF_SPAN; - if (buff_num < CTUCAN_CORE_TXBUF_NUM) { + addr &= ~3; + if ((buff_num < CTUCAN_CORE_TXBUF_NUM) && + (addr < sizeof(s->tx_buffer[buff_num].data))) { uint32_t *bufp = (uint32_t *)(s->tx_buffer[buff_num].data + addr); *bufp = cpu_to_le32(val); }