Re: RFA: libiberty: silence static analyzer warning

[Ian Lance Taylor via Gcc-patches]

On Tue, Mar 16, 2021, 4:48 AM Nick Clifton via Gcc-patches <
gcc-patches@gcc.gnu.org> wrote:

> Hi Ian,
>
>   One of the static analyzers we use is throwing up an error report for
>   one of the libiberty source files:
>
> Error: BUFFER_SIZE (CWE-474):
> libiberty/sha1.c:261: overlapping_buffer: The source buffer
> "&ctx->buffer[16]" potentially overlaps with the destination buffer
> "ctx->buffer", which results in undefined behavior for "memcpy".
> libiberty/sha1.c:261: remediation: Use memmove instead of "memcpy".
> #  259|   sha1_process_block (ctx->buffer, 64, ctx);
> #  260|   left_over -= 64;
> #  261|-> memcpy (ctx->buffer, &ctx->buffer[16], left_over);
> #  262| }
> #  263| ctx->buflen = left_over;
>
>   Looking at the source code I am not sure if the problem can actually
>   be triggered in reality, but there seems to be no harm in being
>   cautious, so I would like to ask for permission to apply the following
>   patch:
>
> diff --git a/libiberty/sha1.c b/libiberty/sha1.c
> index e3d7f86e351..7d15d48d11d 100644
> --- a/libiberty/sha1.c
> +++ b/libiberty/sha1.c
> @@ -258,7 +258,7 @@ sha1_process_bytes (const void *buffer, size_t len,
> struct sha1_ctx *ctx)
> {
>   sha1_process_block (ctx->buffer, 64, ctx);
>   left_over -= 64;
> - memcpy (ctx->buffer, &ctx->buffer[16], left_over);
> + memmove (ctx->buffer, &ctx->buffer[16], left_over);
> }
>ctx->buflen = left_over;
>  }


That is ok.

Thanks.

Ian

>
>

RFA: libiberty: silence static analyzer warning

[Nick Clifton via Gcc-patches]

Hi Ian,

  One of the static analyzers we use is throwing up an error report for
  one of the libiberty source files:

Error: BUFFER_SIZE (CWE-474):
libiberty/sha1.c:261: overlapping_buffer: The source buffer "&ctx->buffer[16]" 
potentially overlaps with the destination buffer "ctx->buffer", which results 
in undefined behavior for "memcpy".
libiberty/sha1.c:261: remediation: Use memmove instead of "memcpy".
#  259|   sha1_process_block (ctx->buffer, 64, ctx);
#  260|   left_over -= 64;
#  261|-> memcpy (ctx->buffer, &ctx->buffer[16], left_over);
#  262| }
#  263| ctx->buflen = left_over;

  Looking at the source code I am not sure if the problem can actually
  be triggered in reality, but there seems to be no harm in being
  cautious, so I would like to ask for permission to apply the following
  patch:

diff --git a/libiberty/sha1.c b/libiberty/sha1.c
index e3d7f86e351..7d15d48d11d 100644
--- a/libiberty/sha1.c
+++ b/libiberty/sha1.c
@@ -258,7 +258,7 @@ sha1_process_bytes (const void *buffer, size_t len, struct 
sha1_ctx *ctx)
{
  sha1_process_block (ctx->buffer, 64, ctx);
  left_over -= 64;
- memcpy (ctx->buffer, &ctx->buffer[16], left_over);
+ memmove (ctx->buffer, &ctx->buffer[16], left_over);
}
   ctx->buflen = left_over;
 }

Cheers
  Nick