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Re: [PATCH v1] sd: sdhci: assert data_count is within fifo_buffer
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH v1] sd: sdhci: assert data_count is within fifo_buffer |
Date: |
Thu, 3 Sep 2020 18:03:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 9/3/20 4:01 PM, Philippe Mathieu-Daudé wrote:
> On 9/3/20 9:08 AM, P J P wrote:
>> From: Prasad J Pandit <pjp@fedoraproject.org>
>>
>> While doing multi block SDMA, transfer block size may exceed
>> the 's->fifo_buffer[s->buf_maxsz]' size. It may leave the
>> current element pointer 's->data_count' pointing out of bounds.
>> Leading the subsequent DMA r/w operation to OOB access issue.
>> Assert that 's->data_count' is within fifo_buffer.
>>
>> ->
>> https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Fsdhci_oob_write1
>> ==1459837==ERROR: AddressSanitizer: heap-buffer-overflow
>> WRITE of size 54722048 at 0x61500001e280 thread T3
>> #0 __interceptor_memcpy (/lib64/libasan.so.6+0x3a71d)
>> #1 flatview_read_continue ../exec.c:3245
>> #2 flatview_read ../exec.c:3278
>> #3 address_space_read_full ../exec.c:3291
>> #4 address_space_rw ../exec.c:3319
>> #5 dma_memory_rw_relaxed ../include/sysemu/dma.h:87
>> #6 dma_memory_rw ../include/sysemu/dma.h:110
>> #7 dma_memory_read ../include/sysemu/dma.h:116
>> #8 sdhci_sdma_transfer_multi_blocks ../hw/sd/sdhci.c:629
>> #9 sdhci_write ../hw/sd/sdhci.c:1097
>> #10 memory_region_write_accessor ../softmmu/memory.c:483
>> ...
>>
>> Reported-by: Ruhr-University <bugs-syssec@rub.de>
>> Suggested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
>> ---
>> hw/sd/sdhci.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> Update v1: use assert(3) calls
>> -> https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg00966.html
>>
>> diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
>> index 1785d7e1f7..023acbed41 100644
>> --- a/hw/sd/sdhci.c
>> +++ b/hw/sd/sdhci.c
>> @@ -604,6 +604,7 @@ static void sdhci_sdma_transfer_multi_blocks(SDHCIState
>> *s)
>> s->blkcnt--;
>> }
>> }
>> + assert(s->data_count <= s->buf_maxsz && s->data_count > begin);
>> dma_memory_write(s->dma_as, s->sdmasysad,
>> &s->fifo_buffer[begin], s->data_count - begin);
>> s->sdmasysad += s->data_count - begin;
>> @@ -626,6 +627,7 @@ static void sdhci_sdma_transfer_multi_blocks(SDHCIState
>> *s)
>> s->data_count = block_size;
>> boundary_count -= block_size - begin;
>> }
>> + assert(s->data_count <= s->buf_maxsz && s->data_count > begin);
>> dma_memory_read(s->dma_as, s->sdmasysad,
>> &s->fifo_buffer[begin], s->data_count - begin);
>> s->sdmasysad += s->data_count - begin;
>>
>
> qemu-system-i386: hw/sd/sdhci.c:632: void
> sdhci_sdma_transfer_multi_blocks(SDHCIState *): Assertion `s->data_count
> <= s->buf_maxsz && s->data_count > begin' failed.
>
> Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>
> If you don't mind I might split the assert in 2 when applying:
>
> - assert(s->data_count <= s->buf_maxsz && s->data_count > begin);
> + assert(s->data_count <= s->buf_maxsz);
> + assert(s->data_count > begin);
Doesn't seem enough, guest crash here, having:
(gdb) p begin
$1 = 0
(gdb) p s->data_count
$2 = 0
(gdb) p s->blksize
$3 = 0
Beh, something is wrong in this model, because when using ADMA2
length 0 means 65536 bytes (see '1.13.4. Descriptor Table' in
"SD Host Controller Simplified Specification Version 2.00").