[PATCH] SUNRPC: fix copying of multiple pages in gss_read_proxy_verf()

[Martijn de Gouw]

When the passed token is longer than 4032 bytes, the remaining part
of the token must be copied from the rqstp->rq_arg.pages. But the
copy must make sure it happens in a consecutive way.

Signed-off-by: Martijn de Gouw <martijn.de.g...@prodrive-technologies.com>
---
 net/sunrpc/auth_gss/svcauth_gss.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c 
b/net/sunrpc/auth_gss/svcauth_gss.c
index 258b04372f85..bd4678db9d76 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -1147,9 +1147,9 @@ static int gss_read_proxy_verf(struct svc_rqst *rqstp,
                               struct gssp_in_token *in_token)
 {
        struct kvec *argv = &rqstp->rq_arg.head[0];
-       unsigned int page_base, length;
-       int pages, i, res;
-       size_t inlen;
+       unsigned int length, pgto_offs, pgfrom_offs;
+       int pages, i, res, pgto, pgfrom;
+       size_t inlen, to_offs, from_offs;
 
        res = gss_read_common_verf(gc, argv, authp, in_handle);
        if (res)
@@ -1177,17 +1177,24 @@ static int gss_read_proxy_verf(struct svc_rqst *rqstp,
        memcpy(page_address(in_token->pages[0]), argv->iov_base, length);
        inlen -= length;
 
-       i = 1;
-       page_base = rqstp->rq_arg.page_base;
+       to_offs = length;
+       from_offs = rqstp->rq_arg.page_base;
        while (inlen) {
-               length = min_t(unsigned int, inlen, PAGE_SIZE);
-               memcpy(page_address(in_token->pages[i]),
-                      page_address(rqstp->rq_arg.pages[i]) + page_base,
+               pgto = to_offs >> PAGE_SHIFT;
+               pgfrom = from_offs >> PAGE_SHIFT;
+               pgto_offs = to_offs & ~PAGE_MASK;
+               pgfrom_offs = from_offs & ~PAGE_MASK;
+
+               length = min_t(unsigned int, inlen,
+                        min_t(unsigned int, PAGE_SIZE - pgto_offs,
+                              PAGE_SIZE - pgfrom_offs));
+               memcpy(page_address(in_token->pages[pgto]) + pgto_offs,
+                      page_address(rqstp->rq_arg.pages[pgfrom]) + pgfrom_offs,
                       length);
 
+               to_offs += length;
+               from_offs += length;
                inlen -= length;
-               page_base = 0;
-               i++;
        }
        return 0;
 }
-- 
2.20.1