Hi
On 19-10-2020 17:23, J. Bruce Fields wrote:
> On Mon, Oct 19, 2020 at 01:42:27PM +0200, Martijn de Gouw wrote:
>> 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.
>
> Thanks. Apologies, but I don't immediately see where the copy is
> non-consecutive. What exactly is the bug in the existing code?
In the first memcpy 'length' bytes are copied from argv->iobase, but
since the header is in front, this never fills the whole first page of
in_token->pages.
The memcpy 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.
Next to that, the remaining data is in page 0 of rqstp->rq_arg.pages,
not page 1.
Regards, Martijn
>
> --b.
>
>>
>> Signed-off-by: Martijn de Gouw <martijn.de.gouw@xxxxxxxxxxxxxxxxxxxxxxxxx>
>> ---
>> 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
--
Martijn de Gouw
Designer
Prodrive Technologies
Mobile: +31 63 17 76 161
Phone: +31 40 26 76 200
