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cadence_gem: Avoid infinite loops with a misconfigured buffer 

A guest can write zero to the DMACFG resulting in an infinite loop when
it reaches the while(bytes_to_copy) loop.

To avoid this issue enforce a minimum size for the RX buffer. Hardware
does not have this enforcement and relies on the guest to set a non-zero
value.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reported-by: Li Qiang <liqiang6-s@360.cn>
Reported-by: P J P <ppandit@redhat.com>
Message-id: 84bb1c391b833275da3f573d4972920cea34c188.1466539342.git.alistair.francis@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Alistair Francis 2016-06-27 15:37:32 +01:00 committed by Peter Maydell
parent f6cf41932e
commit f265ae8c79
1 changed files with 7 additions and 0 deletions
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7
hw/net/cadence_gem.c
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@ -664,6 +664,13 @@ static ssize_t gem_receive(NetClientState *nc, const uint8_t *buf, size_t size)
GEM_DMACFG_RBUFSZ_S) * GEM_DMACFG_RBUFSZ_MUL; GEM_DMACFG_RBUFSZ_S) * GEM_DMACFG_RBUFSZ_MUL;
bytes_to_copy = size; bytes_to_copy = size;
/* Hardware allows a zero value here but warns against it. To avoid QEMU
* indefinite loops we enforce a minimum value here
*/
if (rxbufsize < GEM_DMACFG_RBUFSZ_MUL) {
rxbufsize = GEM_DMACFG_RBUFSZ_MUL;
}
/* Pad to minimum length. Assume FCS field is stripped, logic /* Pad to minimum length. Assume FCS field is stripped, logic
* below will increment it to the real minimum of 64 when * below will increment it to the real minimum of 64 when
* not FCS stripping * not FCS stripping