From: Prasad J Pandit <p...@fedoraproject.org> SMSC91C111 Ethernet interface emulator has registers to store 'packet number' and a 'pointer' to Tx/Rx FIFO buffer area. These two are used to derive an address to access into 'data' registers. If they are set incorrectly, they could lead to an OOB r/w access beyond packet 'data' area. Add check to avoid it.
Reported-by: Azure Yang <azurey...@tencent.com> Signed-off-by: Prasad J Pandit <p...@fedoraproject.org> --- hw/net/smc91c111.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) Update per: add check to _release_packet and for 's->allocated' -> https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg06530.html diff --git a/hw/net/smc91c111.c b/hw/net/smc91c111.c index 3b16dcf..e9b37c2 100644 --- a/hw/net/smc91c111.c +++ b/hw/net/smc91c111.c @@ -203,6 +203,9 @@ static void smc91c111_pop_tx_fifo_done(smc91c111_state *s) /* Release the memory allocated to a packet. */ static void smc91c111_release_packet(smc91c111_state *s, int packet) { + if (packet >= NUM_PACKETS || !(packet & s->allocated)) { + return; + } s->allocated &= ~(1 << packet); if (s->tx_alloc == 0x80) smc91c111_tx_alloc(s); @@ -224,6 +227,9 @@ static void smc91c111_do_tx(smc91c111_state *s) return; for (i = 0; i < s->tx_fifo_len; i++) { packetnum = s->tx_fifo[i]; + if (packetnum >= NUM_PACKETS || !(packetnum & s->allocated)) { + return; + } p = &s->data[packetnum][0]; /* Set status word. */ *(p++) = 0x01; @@ -418,7 +424,7 @@ static void smc91c111_writeb(void *opaque, hwaddr offset, /* Ignore. */ return; case 2: /* Packet Number Register */ - s->packet_num = value; + s->packet_num = value & 0x03F; return; case 3: case 4: case 5: /* Should be readonly, but linux writes to them anyway. Ignore. */ @@ -438,13 +444,17 @@ static void smc91c111_writeb(void *opaque, hwaddr offset, n = s->rx_fifo[0]; else n = s->packet_num; - p = s->ptr & 0x07ff; + p = s->ptr; if (s->ptr & 0x4000) { s->ptr = (s->ptr & 0xf800) | ((s->ptr + 1) & 0x7ff); } else { p += (offset & 3); } - s->data[n][p] = value; + p &= 0x07ff; + if (s->allocated < NUM_PACKETS + && n < NUM_PACKETS && n & s->allocated) { + s->data[n][p] = value; + } } return; case 12: /* Interrupt ACK. */ @@ -517,7 +527,8 @@ static uint32_t smc91c111_readb(void *opaque, hwaddr offset) int i; int n; n = 0; - for (i = 0; i < NUM_PACKETS; i++) { + for (i = 0; + s->allocated < NUM_PACKETS && i < NUM_PACKETS; i++) { if (s->allocated & (1 << i)) n++; } @@ -558,9 +569,9 @@ static uint32_t smc91c111_readb(void *opaque, hwaddr offset) case 0: case 1: /* MMUCR Busy bit. */ return 0; case 2: /* Packet Number. */ - return s->packet_num; + return s->packet_num & 0x3F; case 3: /* Allocation Result. */ - return s->tx_alloc; + return s->tx_alloc < NUM_PACKETS ? s->tx_alloc : 0; case 4: /* TX FIFO */ if (s->tx_fifo_done_len == 0) return 0x80; @@ -584,13 +595,18 @@ static uint32_t smc91c111_readb(void *opaque, hwaddr offset) n = s->rx_fifo[0]; else n = s->packet_num; - p = s->ptr & 0x07ff; + p = s->ptr; if (s->ptr & 0x4000) { s->ptr = (s->ptr & 0xf800) | ((s->ptr + 1) & 0x07ff); } else { p += (offset & 3); } - return s->data[n][p]; + p &= 0x07ff; + if (s->allocated < NUM_PACKETS + && n < NUM_PACKETS && n & s->allocated) { + return s->data[n][p]; + } + return 0; } case 12: /* Interrupt status. */ return s->int_level; -- 2.7.4
