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Added some NULL checks before using strlen(), fixing issue #740 #742

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merged 2 commits into from
Feb 2, 2017
Merged

Added some NULL checks before using strlen(), fixing issue #740 #742

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8f29763
Added some NULL checks before using strlen()
thom-sd Jan 30, 2017
2899708
Undoing some unneccesary checks
thom-sd Feb 1, 2017
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20 changes: 16 additions & 4 deletions userspace/libsinsp/filterchecks.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4427,7 +4427,10 @@ uint8_t* sinsp_filter_check_tracer::extract_arg(sinsp_partial_tracer* pae, OUT u
}
}

*len = strlen(res);
if (res)
{
*len = strlen(res);
}
return (uint8_t*)res;
}

Expand Down Expand Up @@ -4541,7 +4544,10 @@ uint8_t* sinsp_filter_check_tracer::extract(sinsp_evt *evt, OUT uint32_t* len, b
}
}

*len = strlen(res);
if(res)
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The fix makes sense since from the if above res may be not initialised, have you found any reasons why? Is it expected?

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If the m_argid is somehow out of range, res will not get initialized. This is basically the same as some of the code that we crashed on further below. I'm not entirely sure yet why m_argid would be out of range but reading the code it seems acceptable to just return NULL, so the added strlen() should not assume res is set.
In general I'm a big proponent of more defensive programming. In cases like this it would only add very few cycles to sanity check, but may help prevent more core dumps in the future.

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yes let's do it, for sure more sanity check does not hurt.

{
*len = strlen(res);
}
return (uint8_t*)res;
}
case TYPE_IDTAG:
Expand Down Expand Up @@ -5030,7 +5036,10 @@ inline uint8_t* sinsp_filter_check_evtin::extract_tracer(sinsp_evt *evt, sinsp_p
}
}

*len = strlen(val);
if(val)
{
*len = strlen(val);
}
return (uint8_t*) val;
}
case TYPE_ARGS:
Expand Down Expand Up @@ -5123,7 +5132,10 @@ inline uint8_t* sinsp_filter_check_evtin::extract_tracer(sinsp_evt *evt, sinsp_p
}
}

*len = strlen(val);
if(val)
{
*len = strlen(val);
}
return (uint8_t*) val;
}
default:
Expand Down