Re: [PATCH] libbacktrace: fix UBSAN issues

["Martin Liška" <mliska@suse.cz>]

On 11/11/21 20:21, Ian Lance Taylor wrote:
> On Thu, Nov 11, 2021 at 7:39 AM Martin Liška <mliska@suse.cz> wrote:
>>
>> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>>
>> Ready to be installed?
>> Thanks,
>> Martin
>>
>> Fix issues mentioned in the PR.
>>
>>          PR libbacktrace/103167
>>
>> libbacktrace/ChangeLog:
>>
>>          * elf.c (elf_uncompress_lzma_block): Cast to unsigned int.
>>          (elf_uncompress_lzma): Likewise.
>>          * xztest.c (test_samples): memcpy only if v > 0.
>>
>> Co-Authored-By: Andrew Pinski <apinski@marvell.com>
>> ---
>>    libbacktrace/elf.c    | 8 ++++----
>>    libbacktrace/xztest.c | 2 +-
>>    2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/libbacktrace/elf.c b/libbacktrace/elf.c
>> index 79d56146fc6..e69ac41c88b 100644
>> --- a/libbacktrace/elf.c
>> +++ b/libbacktrace/elf.c
>> @@ -3175,7 +3175,7 @@ elf_uncompress_lzma_block (const unsigned char *compressed,
>>      stream_crc = (compressed[off]
>>                  | (compressed[off + 1] << 8)
>>                  | (compressed[off + 2] << 16)
>> -               | (compressed[off + 3] << 24));
>> +               | ((unsigned)(compressed[off + 3]) << 24));
> 
> Thanks, but this kind of thing looks strange and is therefore likely
> to break again in the future.  I suggest instead
> 
>    stream_crc = ((uint32_t) compressed[off]
>                           | ((uint32_t) compressed[off + 1] << 8)
>                           | ((uint32_t) compressed[off + 2] << 16)
>                           | ((uint32_t) compressed[off + 3] << 24));
> 
> Same for the similar cases elsewhere.

Sure, done and pushed as g:83310a08a2bc52b6e8c3a3e3216b4e723e58c961.

Thanks,
Martin

> 
> Ian
>