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SubjectRe: [SIL2review] [PATCH] fixdep: free memory on second error path of do_config_file

On Mon, 18 Dec 2017, Masahiro Yamada wrote:

> 2017-12-15 17:23 GMT+09:00 Nicholas Mc Guire <der.herr@hofr.at>:
>> On Thu, Dec 14, 2017 at 08:54:10PM +0100, Lukas Bulwahn wrote:
>>> Commit dee81e988674 ("fixdep: faster CONFIG_ search") introduces the memory
>>> leak when `map = mmap(...)` was replaced with `map = malloc(...)` and
>>> `read(fd, map, ...)`. It introduces a new second error path, which does not
>>> free the allocated memory for `map`. We now correct that behavior and free
>>> `map` before the do_config_file() function returns.
>>>
>>> Facebook's static analysis tool Infer (http://fbinfer.com) found this
>>> memory leak:
>>>
>>> scripts/basic/fixdep.c:297: error: MEMORY_LEAK
>>> memory dynamically allocated by call to `malloc()` at line 290, \
>>> column 8 is not reachable after line 297, column 3.
>>>
>>> Fixes: dee81e988674 ("fixdep: faster CONFIG_ search")
>>>
>>> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
>> Reviewed-by: Nicholas Mc Guire <der.herr@hofr.at>
>>
>>> ---
>>> scripts/basic/fixdep.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
>>> index bbf62cb..131c450 100644
>>> --- a/scripts/basic/fixdep.c
>>> +++ b/scripts/basic/fixdep.c
>>> @@ -296,6 +296,7 @@ static void do_config_file(const char *filename)
>>> if (read(fd, map, st.st_size) != st.st_size) {
>>> perror("fixdep: read");
>>> close(fd);
>>> + free(map);
>>
>> This looks reasonable but actually it is not clear why do_config_file()
>> should return at all if read fails as the read error would go unnoticed
>> in the current code and allow the build to continue. so this probably
>> should be an exit(2) here and not a return which would then take care
>> of the free() anyway.
>
> I agree.
>
> This should be exit(2).
>
> You can also remove close() as well since
> the operation system will close it anyway.
>
>
>
>> Atleast I do not see the rational to allow continuation if the read
>> failed as the file should not be empty nor a mismatch with st.st_size
>> expected. If it were due to a EINTR then it still should terminate as
>> EINTR was not handled and we thus could miss a valid dependency.
>>
>> Note: this probably also should be applied to the if (!map) condition
>> before as well, as at that point it is known that map > 0 and a malloc()
>> failure would allow skipping parse_config_file() for a valid config.
>
> I agree. We should change this too.
>

I created a new patch with your requested changes, but I did not consider
it a second version of this patch by the time of writing. You can find the
new patch at:

v1: https://patchwork.kernel.org/patch/10126547/
v2: https://patchwork.kernel.org/patch/10128297/

This patch here is now superseded by the new patch. So, this patch here
can be abandoned.

Lukas

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