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From: | Anthony Liguori |
Subject: | [Qemu-devel] Re: [PATCH RFC] e1000: fix access 4 bytes beyond buffer end |
Date: | Mon, 12 Jul 2010 18:00:20 -0500 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100528 Lightning/1.0b1 Thunderbird/3.0.5 |
On 07/12/2010 05:42 PM, Michael S. Tsirkin wrote:
On Mon, Jul 12, 2010 at 04:07:21PM -0500, Anthony Liguori wrote:On 07/12/2010 12:48 PM, Michael S. Tsirkin wrote:We do range check for size, and get size as buffer, but copy size + 4 bytes (4 is for FCS). Let's copy size bytes but put size + 4 in length. Signed-off-by: Michael S. Tsirkin<address@hidden>I think I'd feel slightly better if we zero'd out the FCS before writing it to the guest. It is potentially a data leak. Regards, Anthony LiguoriI am guessing there's no chance guest actually looks at this data, otherwise it won't match and we'd get errors, right?
That's my assumption too. Although I believe there are some known issues with e1000 and certain versions of Windows and the Microsoft built-in driver. Maybe this is why those drivers don't work and the Intel drivers do?
Regards, Anthony Liguori
--- Anthony, Alex, please review. hw/e1000.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/hw/e1000.c b/hw/e1000.c index 0da65f9..70aba11 100644 --- a/hw/e1000.c +++ b/hw/e1000.c @@ -649,7 +649,6 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) } rdh_start = s->mac_reg[RDH]; - size += 4; // for the header do { if (s->mac_reg[RDH] == s->mac_reg[RDT]&& s->check_rxov) { set_ics(s, 0, E1000_ICS_RXO); @@ -663,7 +662,7 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) if (desc.buffer_addr) { cpu_physical_memory_write(le64_to_cpu(desc.buffer_addr), (void *)(buf + vlan_offset), size); - desc.length = cpu_to_le16(size); + desc.length = cpu_to_le16(size + 4 /* for FCS */); desc.status |= E1000_RXD_STAT_EOP|E1000_RXD_STAT_IXSM; } else // as per intel docs; skip descriptors with null buf addr DBGOUT(RX, "Null RX descriptor!!\n");
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