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    Subject[PATCH 5.9 558/757] SUNRPC: fix copying of multiple pages in gss_read_proxy_verf()
    Date
    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 258b04372f854..bd4678db9d76b 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;
    }
    --
    2.25.1


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