Re: [PATCH] scsi: Silence gcc warning

[Eric Blake]

Adding qemu-trivial in cc.

On 2/9/21 9:44 AM, Philippe Mathieu-Daudé wrote:
> On 2/9/21 4:23 PM, Eric Blake wrote:
>> On Fedora 33, gcc 10.2.1 notes that scsi_cdb_length(buf) can set
>> len==-1, which in turn overflows g_malloc():
>>
>> [5/5] Linking target qemu-system-x86_64
>> In function ‘scsi_disk_new_request_dump’,
>>     inlined from ‘scsi_new_request’ at ../hw/scsi/scsi-disk.c:2608:9:
>> ../hw/scsi/scsi-disk.c:2582:19: warning: argument 1 value 
>> ‘18446744073709551612’ exceeds maximum object size 9223372036854775807 
>> [-Walloc-size-larger-than=]
>>  2582 |     line_buffer = g_malloc(len * 5 + 1);
>>       |                   ^
>>
>> Silence it with a decent assertion, since we only convert a buffer to
>> bytes when we have a valid cdb length.
>>
>> Signed-off-by: Eric Blake <eblake@redhat.com>
>> ---
>>  hw/scsi/scsi-disk.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
>> index ed52fcd49ff0..b3311a5657b7 100644
>> --- a/hw/scsi/scsi-disk.c
>> +++ b/hw/scsi/scsi-disk.c
>> @@ -2579,6 +2579,7 @@ static void scsi_disk_new_request_dump(uint32_t lun, 
>> uint32_t tag, uint8_t *buf)
>>      int len = scsi_cdb_length(buf);
>>      char *line_buffer, *p;
>>
>> +    assert(len > 0 && len <= 16);
>>      line_buffer = g_malloc(len * 5 + 1);
>>
>>      for (i = 0, p = line_buffer; i < len; i++) {
>>
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org