crypto: scatterwalk - Check for same address in map_and_copy

This patch adds a check for in scatterwalk_map_and_copy to avoid
copying from the same address to the same address.  This is going
to be used for IV copying in AEAD IV generators.

There is no provision for partial overlaps.

This patch also uses the new scatterwalk_ffwd instead of doing
it by hand in scatterwalk_map_and_copy.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index db920b59a6c3332fdb771a5bcc0b0c338fce3d95..8690324d3aefdcbf4ab428b26e56efe25792726b 100644 (file)
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -104,22 +104,18 @@ void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
                              unsigned int start, unsigned int nbytes, int out)
 {
        struct scatter_walk walk;
-       unsigned int offset = 0;
+       struct scatterlist tmp[2];
 
        if (!nbytes)
                return;
 
-       for (;;) {
-               scatterwalk_start(&walk, sg);
-
-               if (start < offset + sg->length)
-                       break;
+       sg = scatterwalk_ffwd(tmp, sg, start);
 
-               offset += sg->length;
-               sg = sg_next(sg);
-       }
+       if (sg_page(sg) == virt_to_page(buf) &&
+           sg->offset == offset_in_page(buf))
+               return;
 
-       scatterwalk_advance(&walk, start - offset);
+       scatterwalk_start(&walk, sg);
        scatterwalk_copychunks(buf, &walk, nbytes, out);
        scatterwalk_done(&walk, out, 0);
 }