From 2a6cb383e2ec7224d8631c3c0a324bff469c9c64 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 24 Aug 2023 16:32:21 +0100 Subject: [PATCH] hw/net/fsl_etsec/rings.c: Avoid variable length array MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In fill_rx_bd() we create a variable length array of size etsec->rx_padding. In fact we know that this will never be larger than 64 bytes, because rx_padding is set in rx_init_frame() in a way that ensures it is only that large. Use a fixed sized array and assert that it is big enough. Since padd[] is now potentially rather larger than the actual padding required, adjust the memset() we do on it to match the size that we write with cpu_physical_memory_write(), rather than clearing the entire array. The codebase has very few VLAs, and if we can get rid of them all we can make the compiler error on new additions. This is a defensive measure against security bugs where an on-stack dynamic allocation isn't correctly size-checked (e.g. CVE-2021-3527). Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Jason Wang --- hw/net/fsl_etsec/rings.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/hw/net/fsl_etsec/rings.c b/hw/net/fsl_etsec/rings.c index 788463f1b6..2f2f359f7a 100644 --- a/hw/net/fsl_etsec/rings.c +++ b/hw/net/fsl_etsec/rings.c @@ -372,6 +372,12 @@ void etsec_walk_tx_ring(eTSEC *etsec, int ring_nbr) etsec->regs[TSTAT].value |= 1 << (31 - ring_nbr); } +/* + * rx_init_frame() ensures we never do more padding than this + * (checksum plus minimum data packet size) + */ +#define MAX_RX_PADDING 64 + static void fill_rx_bd(eTSEC *etsec, eTSEC_rxtx_bd *bd, const uint8_t **buf, @@ -380,9 +386,11 @@ static void fill_rx_bd(eTSEC *etsec, uint16_t to_write; hwaddr bufptr = bd->bufptr + ((hwaddr)(etsec->regs[TBDBPH].value & 0xF) << 32); - uint8_t padd[etsec->rx_padding]; + uint8_t padd[MAX_RX_PADDING]; uint8_t rem; + assert(etsec->rx_padding <= MAX_RX_PADDING); + RING_DEBUG("eTSEC fill Rx buffer @ 0x%016" HWADDR_PRIx " size:%zu(padding + crc:%u) + fcb:%u\n", bufptr, *size, etsec->rx_padding, etsec->rx_fcb_size); @@ -426,7 +434,7 @@ static void fill_rx_bd(eTSEC *etsec, rem = MIN(etsec->regs[MRBLR].value - bd->length, etsec->rx_padding); if (rem > 0) { - memset(padd, 0x0, sizeof(padd)); + memset(padd, 0x0, rem); etsec->rx_padding -= rem; *size -= rem; bd->length += rem;