Re: [Valgrind-users] How to write a tool to check unsafe strcpy-alike functions in another way

[Дмитрий Д. <di...@gm...>]

Hi!

exp-sgcheck can't help?

Dmitry

2013/10/31 Philippe Waroquiers <phi...@sk...>:
> On Thu, 2013-10-31 at 15:26 +0330, hamid alaei wrote:
>> Hi everyone,
>> Assume there is a C code that do this:
>>
>>
>> char buff1[20];
>> char buff2[30]="some small string";
>> ...
>>
>> strcpy(buff1, buff2);
>>
>>
>>
>> This code is can be regarded unsafe not only because it use strcpy(),
>> which doesn't accept a size argument for the maximum capacity of
>> buff1, but also because the maximum capacity if the target string
>> buff1 is less than the maximum capacity of the src string buff2.
>>
>> I know that if strcpy() tries to write outside buff1, then memcheck or
>> sgcheck can detect that, depending on whether these strings are in
>> stack/global memory or in the heap. But I want a warning while calling
>> strcpy() in this manner as well, regardless of whether overflow
>> happens or not.
>>
>>
>> I am wondering if there is such a tool to do so. I guess it should
>> replace strcpy() and similar functions with a wrapper. Does anybody
>> know suck a tool/extension or how to write such a wrapper that can
>> have access to the max-size of buff1 and buff2?
>
> This might be an interesting addition to e.g. memcheck
> (or other tools that are replacing str* and others functions).
>
> I think this will be relatively easy to do for "simple cases"
> of stack and global arrays, and maybe arrays in a stack/global struct :
> using --read-var-info=yes, valgrind provides access to (some)
> information about theses, (and from a small experiment, it looks
> like it knows the size of these).
>
> However, for more complex cases (e.g. arrays in a dynamically allocated
> struct), this will be more complex: how to guess (or keep track) that a
> pointer inside a block is a pointer to an array smaller than
> the malloc-ed block is unclear to me.
>
> Philippe
>
>
>
>
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