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Re: Commit: Use of alloca considered dangerous

> On Mar 21, 2016, at 12:58 PM, Jeff Law <> wrote:
> On 03/21/2016 10:56 AM, wrote:
>>> On Mar 21, 2016, at 12:30 PM, Nick Clifton <> wrote:
>>> Hi Guys,
>>>  It was pointed out to me the other day that there are some unbounded
>>>  calls to alloca in the binutils, which in theory could lead to
>>>  exploits.  So I tried adding -Wstack-usage=NNN to the command line and
>>>  discovered that gcc would complain about any use of alloca, even
>>>  bounded ones.  Still they were easy to fix, and removing the use of
>>>  alloca, and variable length local arrays as well, seems like a good
>>>  idea.
>> I agree that alloca() needs bounds checks, but I don't see why you say that avoiding alloca entirely is "a good idea".
> Based on what I've seen through the years, if you can't put a hard bounds on an alloca, then you're far better off from a security standpoint avoiding it completely.

Absolutely.  But isn't that a case by case test?  If 7 uses of alloca don't have a guaranteed hard bound but the 8th one does, then I agree the 7 have to change -- but would it not be reasonable to keep the 8th?


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