[PATCH 5.4 283/408] SUNRPC: fix copying of multiple pages in gss_read_proxy_verf()

Greg Kroah-Hartman
2020-10-27T17:06:31Z

From: Martijn de Gouw <martijn.de.gouw@prodrive-technologies.com>

[ Upstream commit d48c8124749c9a5081fe68680f83605e272c984b ]

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.

With the existing code, the first memcpy copies 'length' bytes from
argv->iobase, but since the header is in front, this never fills the
whole first page of in_token->pages.

The mecpy in the loop copies the following bytes, but starts writing at
the next page of in_token->pages. This leaves the last bytes of page 0
unwritten.

Symptoms were that users with many groups were not able to access NFS
exports, when using Active Directory as the KDC.

Signed-off-by: Martijn de Gouw <martijn.de.gouw@prodrive-technologies.com>
Fixes: 5866efa8cbfb "SUNRPC: Fix svcauth_gss_proxy_init()"
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 3645cd241d3ea..cf4d6d7e72822 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -1095,9 +1095,9 @@ 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)
@@ -1125,17 +1125,24 @@ 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;
}
--
2.25.1