diff mbox

[V4] xdrstdio_create buffers do not output encoded values on ppc

Message ID 20180711152521.8238-1-steved@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Steve Dickson July 11, 2018, 3:25 p.m. UTC
The cause is that the xdr_putlong uses a long to store the
converted value, then passes it to fwrite as a byte buffer.
Only the first 4 bytes are written, which is okay for a LE
system after byteswapping, but writes all zeroes on BE systems.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>
---
v4: Use UINT32_MAX instead of INT32_MAX in boundary check.

v3: Reworked the bounds checking

v2: Added bounds checking
    Changed from unsigned to signed

 src/xdr_stdio.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Comments

Steve Dickson July 11, 2018, 4:05 p.m. UTC | #1
Hey Trond,

On 07/11/2018 11:25 AM, Steve Dickson wrote:
> The cause is that the xdr_putlong uses a long to store the
> converted value, then passes it to fwrite as a byte buffer.
> Only the first 4 bytes are written, which is okay for a LE
> system after byteswapping, but writes all zeroes on BE systems.
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738
> 
> Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
> Signed-off-by: Steve Dickson <steved@redhat.com>
> ---
> v4: Use UINT32_MAX instead of INT32_MAX in boundary check.
Talking with some old crusty types ;-) they pointed out
that all these routines use a signed arguments and
always have... So again why is using an unsigned max
the right thing to do? 

steved.
  
> 
> v3: Reworked the bounds checking
> 
> v2: Added bounds checking
>     Changed from unsigned to signed
> 
>  src/xdr_stdio.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c
> index 4410262..846c7bf 100644
> --- a/src/xdr_stdio.c
> +++ b/src/xdr_stdio.c
> @@ -38,6 +38,7 @@
>   */
>  
>  #include <stdio.h>
> +#include <stdint.h>
>  
>  #include <arpa/inet.h>
>  #include <rpc/types.h>
> @@ -103,10 +104,12 @@ xdrstdio_getlong(xdrs, lp)
>  	XDR *xdrs;
>  	long *lp;
>  {
> +	int32_t mycopy;
>  
> -	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
> +	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
>  		return (FALSE);
> -	*lp = (long)ntohl((u_int32_t)*lp);
> +
> +	*lp = (long)ntohl(mycopy);
>  	return (TRUE);
>  }
>  
> @@ -115,8 +118,14 @@ xdrstdio_putlong(xdrs, lp)
>  	XDR *xdrs;
>  	const long *lp;
>  {
> -	long mycopy = (long)htonl((u_int32_t)*lp);
> +	int32_t mycopy;
> +
> +#if defined(_LP64)
> +	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))
> +		return (FALSE);
> +#endif
>  
> +	mycopy = (int32_t)htonl((int32_t)*lp);
>  	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
>  		return (FALSE);
>  	return (TRUE);
> 
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Trond Myklebust July 11, 2018, 4:38 p.m. UTC | #2
On Wed, 2018-07-11 at 12:05 -0400, Steve Dickson wrote:
> Hey Trond,

> 

> On 07/11/2018 11:25 AM, Steve Dickson wrote:

> > The cause is that the xdr_putlong uses a long to store the

> > converted value, then passes it to fwrite as a byte buffer.

> > Only the first 4 bytes are written, which is okay for a LE

> > system after byteswapping, but writes all zeroes on BE systems.

> > 

> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738

> > 

> > Reviewed-by: Chuck Lever <chuck.lever@oracle.com>

> > Signed-off-by: Steve Dickson <steved@redhat.com>

> > ---

> > v4: Use UINT32_MAX instead of INT32_MAX in boundary check.

> 

> Talking with some old crusty types ;-) they pointed out

> that all these routines use a signed arguments and

> always have... So again why is using an unsigned max

> the right thing to do? 


As I said earlier, you are casting from a larger type to a smaller
type, and you want it to work for both signed and unsigned 32-bit
values. Consider this kind of code:

        int32_t foo = 0xFFFF0000;
        ret = xdrstdio_putlong(xdr, foo);

Since foo is signed, then (long)foo ends up getting cast to
0xFFFFFFFFFFFF0000L, which is negative, but is > (long)INT32_MIN. So
ret == TRUE;


Now try:

        uint32_t bar = 0xFFFF0000U;
        ret = xdrstdio_putlong(xdr, bar);


Since bar is unsigned, then (long)bar gets cast to 0xFFFF0000L. That is
clearly > (long)INT32_MAX == 0x7FFFFFFFL, and so the above fails with
ret == FALSE.


BTW: The above is pretty much exactly how xdr_int32_t() and
xdr_uint32_t() work. The former does a signed cast to long, while the
latter does an unsigned cast to long.


> 

> steved.

>   

> > 

> > v3: Reworked the bounds checking

> > 

> > v2: Added bounds checking

> >     Changed from unsigned to signed

> > 

> >  src/xdr_stdio.c | 15 ++++++++++++---

> >  1 file changed, 12 insertions(+), 3 deletions(-)

> > 

> > diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c

> > index 4410262..846c7bf 100644

> > --- a/src/xdr_stdio.c

> > +++ b/src/xdr_stdio.c

> > @@ -38,6 +38,7 @@

> >   */

> >  

> >  #include <stdio.h>

> > +#include <stdint.h>

> >  

> >  #include <arpa/inet.h>

> >  #include <rpc/types.h>

> > @@ -103,10 +104,12 @@ xdrstdio_getlong(xdrs, lp)

> >  	XDR *xdrs;

> >  	long *lp;

> >  {

> > +	int32_t mycopy;

> >  

> > -	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs->x_private) 

> > != 1)

> > +	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-

> > >x_private) != 1)

> >  		return (FALSE);

> > -	*lp = (long)ntohl((u_int32_t)*lp);

> > +

> > +	*lp = (long)ntohl(mycopy);

> >  	return (TRUE);

> >  }

> >  

> > @@ -115,8 +118,14 @@ xdrstdio_putlong(xdrs, lp)

> >  	XDR *xdrs;

> >  	const long *lp;

> >  {

> > -	long mycopy = (long)htonl((u_int32_t)*lp);

> > +	int32_t mycopy;

> > +

> > +#if defined(_LP64)

> > +	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))

> > +		return (FALSE);

> > +#endif

> >  

> > +	mycopy = (int32_t)htonl((int32_t)*lp);

> >  	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-

> > >x_private) != 1)

> >  		return (FALSE);

> >  	return (TRUE);

> > 

> 

> --

> To unsubscribe from this list: send the line "unsubscribe linux-nfs"

> in

> the body of a message to majordomo@vger.kernel.org

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-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com
Chuck Lever III July 11, 2018, 6:06 p.m. UTC | #3
> On Jul 11, 2018, at 12:38 PM, Trond Myklebust <trondmy@hammerspace.com> wrote:
> 
> On Wed, 2018-07-11 at 12:05 -0400, Steve Dickson wrote:
>> Hey Trond,
>> 
>> On 07/11/2018 11:25 AM, Steve Dickson wrote:
>>> The cause is that the xdr_putlong uses a long to store the
>>> converted value, then passes it to fwrite as a byte buffer.
>>> Only the first 4 bytes are written, which is okay for a LE
>>> system after byteswapping, but writes all zeroes on BE systems.
>>> 
>>> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738
>>> 
>>> Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
>>> Signed-off-by: Steve Dickson <steved@redhat.com>
>>> ---
>>> v4: Use UINT32_MAX instead of INT32_MAX in boundary check.
>> 
>> Talking with some old crusty types ;-) they pointed out
>> that all these routines use a signed arguments and
>> always have... So again why is using an unsigned max
>> the right thing to do? 
> 
> As I said earlier, you are casting from a larger type to a smaller
> type, and you want it to work for both signed and unsigned 32-bit
> values. Consider this kind of code:
> 
>        int32_t foo = 0xFFFF0000;
>        ret = xdrstdio_putlong(xdr, foo);
> 
> Since foo is signed, then (long)foo ends up getting cast to
> 0xFFFFFFFFFFFF0000L, which is negative, but is > (long)INT32_MIN. So
> ret == TRUE;

On 32-bit systems, xdrstdio_putlong() cannot work for values
between INT32_MAX and UINT32_MAX. It should return FALSE for
these values on 64-bit systems. In fact, that is the way this
API behaves for other 64-bit aware libtirpc implementations.


> Now try:
> 
>        uint32_t bar = 0xFFFF0000U;
>        ret = xdrstdio_putlong(xdr, bar);
> 
> 
> Since bar is unsigned, then (long)bar gets cast to 0xFFFF0000L. That is
> clearly > (long)INT32_MAX == 0x7FFFFFFFL, and so the above fails with
> ret == FALSE.
> 
> 
> BTW: The above is pretty much exactly how xdr_int32_t() and
> xdr_uint32_t() work. The former does a signed cast to long, while the
> latter does an unsigned cast to long.

If that's the case, we should examine how other 64-bit aware
libtirpc implementations work and fix ours to behave the same.
Our libtirpc forked in the late 1990s before 64-bit systems
were widely deployed, so I have some doubts whether our
implementation is correct.


>> steved.
>> 
>>> 
>>> v3: Reworked the bounds checking
>>> 
>>> v2: Added bounds checking
>>>    Changed from unsigned to signed
>>> 
>>> src/xdr_stdio.c | 15 ++++++++++++---
>>> 1 file changed, 12 insertions(+), 3 deletions(-)
>>> 
>>> diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c
>>> index 4410262..846c7bf 100644
>>> --- a/src/xdr_stdio.c
>>> +++ b/src/xdr_stdio.c
>>> @@ -38,6 +38,7 @@
>>>  */
>>> 
>>> #include <stdio.h>
>>> +#include <stdint.h>
>>> 
>>> #include <arpa/inet.h>
>>> #include <rpc/types.h>
>>> @@ -103,10 +104,12 @@ xdrstdio_getlong(xdrs, lp)
>>> 	XDR *xdrs;
>>> 	long *lp;
>>> {
>>> +	int32_t mycopy;
>>> 
>>> -	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs->x_private) 
>>> != 1)
>>> +	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-
>>>> x_private) != 1)
>>> 		return (FALSE);
>>> -	*lp = (long)ntohl((u_int32_t)*lp);
>>> +
>>> +	*lp = (long)ntohl(mycopy);
>>> 	return (TRUE);
>>> }
>>> 
>>> @@ -115,8 +118,14 @@ xdrstdio_putlong(xdrs, lp)
>>> 	XDR *xdrs;
>>> 	const long *lp;
>>> {
>>> -	long mycopy = (long)htonl((u_int32_t)*lp);
>>> +	int32_t mycopy;
>>> +
>>> +#if defined(_LP64)
>>> +	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))
>>> +		return (FALSE);
>>> +#endif
>>> 
>>> +	mycopy = (int32_t)htonl((int32_t)*lp);
>>> 	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-
>>>> x_private) != 1)
>>> 		return (FALSE);
>>> 	return (TRUE);
>>> 
>> 
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-nfs"
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
> 
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> Libtirpc-devel mailing list
> Libtirpc-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/libtirpc-devel

--
Chuck Lever



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Trond Myklebust July 11, 2018, 6:19 p.m. UTC | #4
On Wed, 2018-07-11 at 14:06 -0400, Chuck Lever wrote:
> > On Jul 11, 2018, at 12:38 PM, Trond Myklebust <trondmy@hammerspace.

> > com> wrote:

> > 

> > On Wed, 2018-07-11 at 12:05 -0400, Steve Dickson wrote:

> > > Hey Trond,

> > > 

> > > On 07/11/2018 11:25 AM, Steve Dickson wrote:

> > > > The cause is that the xdr_putlong uses a long to store the

> > > > converted value, then passes it to fwrite as a byte buffer.

> > > > Only the first 4 bytes are written, which is okay for a LE

> > > > system after byteswapping, but writes all zeroes on BE systems.

> > > > 

> > > > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738

> > > > 

> > > > Reviewed-by: Chuck Lever <chuck.lever@oracle.com>

> > > > Signed-off-by: Steve Dickson <steved@redhat.com>

> > > > ---

> > > > v4: Use UINT32_MAX instead of INT32_MAX in boundary check.

> > > 

> > > Talking with some old crusty types ;-) they pointed out

> > > that all these routines use a signed arguments and

> > > always have... So again why is using an unsigned max

> > > the right thing to do? 

> > 

> > As I said earlier, you are casting from a larger type to a smaller

> > type, and you want it to work for both signed and unsigned 32-bit

> > values. Consider this kind of code:

> > 

> >        int32_t foo = 0xFFFF0000;

> >        ret = xdrstdio_putlong(xdr, foo);

> > 

> > Since foo is signed, then (long)foo ends up getting cast to

> > 0xFFFFFFFFFFFF0000L, which is negative, but is > (long)INT32_MIN.

> > So

> > ret == TRUE;

> 

> On 32-bit systems, xdrstdio_putlong() cannot work for values

> between INT32_MAX and UINT32_MAX. It should return FALSE for

> these values on 64-bit systems. In fact, that is the way this

> API behaves for other 64-bit aware libtirpc implementations.


On a 32-bit system there is no need to check anything, because
sizeof(long) == sizeof(int) == 4.

The problems occur once you start casting from a smaller sized integer
to a larger one because the unsigned cast will behave differently to
the signed cast and result in a bitwise very different value.

> > Now try:

> > 

> >        uint32_t bar = 0xFFFF0000U;

> >        ret = xdrstdio_putlong(xdr, bar);

> > 

> > 

> > Since bar is unsigned, then (long)bar gets cast to 0xFFFF0000L.

> > That is

> > clearly > (long)INT32_MAX == 0x7FFFFFFFL, and so the above fails

> > with

> > ret == FALSE.

> > 

> > 

> > BTW: The above is pretty much exactly how xdr_int32_t() and

> > xdr_uint32_t() work. The former does a signed cast to long, while

> > the

> > latter does an unsigned cast to long.

> 

> If that's the case, we should examine how other 64-bit aware

> libtirpc implementations work and fix ours to behave the same.

> Our libtirpc forked in the late 1990s before 64-bit systems

> were widely deployed, so I have some doubts whether our

> implementation is correct.


Observe:

bool_t
xdr_int32_t(xdrs, int32_p)
        XDR *xdrs;
        int32_t *int32_p;
{
        long l;

        switch (xdrs->x_op) {

        case XDR_ENCODE:
                l = (long) *int32_p;
                return (XDR_PUTLONG(xdrs, &l));

        case XDR_DECODE:
                if (!XDR_GETLONG(xdrs, &l)) {
                        return (FALSE);
                }
                *int32_p = (int32_t) l;
                return (TRUE);

        case XDR_FREE:
                return (TRUE);
        }
        /* NOTREACHED */
        return (FALSE);
}

bool_t
xdr_u_int32_t(xdrs, u_int32_p)
        XDR *xdrs;
        u_int32_t *u_int32_p;
{
        u_long l;

        switch (xdrs->x_op) {

        case XDR_ENCODE:
                l = (u_long) *u_int32_p;
                return (XDR_PUTLONG(xdrs, (long *)&l));

        case XDR_DECODE:
                if (!XDR_GETLONG(xdrs, (long *)&l)) {
                        return (FALSE);
                }
                *u_int32_p = (u_int32_t) l;
                return (TRUE);

        case XDR_FREE:
                return (TRUE);
        }
        /* NOTREACHED */
        return (FALSE);
}

> > > steved.

> > > 

> > > > 

> > > > v3: Reworked the bounds checking

> > > > 

> > > > v2: Added bounds checking

> > > >    Changed from unsigned to signed

> > > > 

> > > > src/xdr_stdio.c | 15 ++++++++++++---

> > > > 1 file changed, 12 insertions(+), 3 deletions(-)

> > > > 

> > > > diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c

> > > > index 4410262..846c7bf 100644

> > > > --- a/src/xdr_stdio.c

> > > > +++ b/src/xdr_stdio.c

> > > > @@ -38,6 +38,7 @@

> > > >  */

> > > > 

> > > > #include <stdio.h>

> > > > +#include <stdint.h>

> > > > 

> > > > #include <arpa/inet.h>

> > > > #include <rpc/types.h>

> > > > @@ -103,10 +104,12 @@ xdrstdio_getlong(xdrs, lp)

> > > > 	XDR *xdrs;

> > > > 	long *lp;

> > > > {

> > > > +	int32_t mycopy;

> > > > 

> > > > -	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs-

> > > > >x_private) 

> > > > != 1)

> > > > +	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-

> > > > > x_private) != 1)

> > > > 

> > > > 		return (FALSE);

> > > > -	*lp = (long)ntohl((u_int32_t)*lp);

> > > > +

> > > > +	*lp = (long)ntohl(mycopy);

> > > > 	return (TRUE);

> > > > }

> > > > 

> > > > @@ -115,8 +118,14 @@ xdrstdio_putlong(xdrs, lp)

> > > > 	XDR *xdrs;

> > > > 	const long *lp;

> > > > {

> > > > -	long mycopy = (long)htonl((u_int32_t)*lp);

> > > > +	int32_t mycopy;

> > > > +

> > > > +#if defined(_LP64)

> > > > +	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))

> > > > +		return (FALSE);

> > > > +#endif

> > > > 

> > > > +	mycopy = (int32_t)htonl((int32_t)*lp);

> > > > 	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-

> > > > > x_private) != 1)

> > > > 

> > > > 		return (FALSE);

> > > > 	return (TRUE);

> > > > 

> > > 

> > > --

> > > To unsubscribe from this list: send the line "unsubscribe linux-

> > > nfs"

> > > in

> > > the body of a message to majordomo@vger.kernel.org

> > > More majordomo info at  http://vger.kernel.org/majordomo-info.htm

> > > l

> > 

> > -- 

> > Trond Myklebust

> > Linux NFS client maintainer, Hammerspace

> > trond.myklebust@hammerspace.com

> > 

> > -----------------------------------------------------------------

> > -------------

> > Check out the vibrant tech community on one of the world's most

> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot

> > _______________________________________________

> > Libtirpc-devel mailing list

> > Libtirpc-devel@lists.sourceforge.net

> > https://lists.sourceforge.net/lists/listinfo/libtirpc-devel

> 

> --

> Chuck Lever

> 

> 

> 

-- 
Trond Myklebust
CTO, Hammerspace Inc
4300 El Camino Real, Suite 105
Los Altos, CA 94022
www.hammer.space
Chuck Lever III July 11, 2018, 8:42 p.m. UTC | #5
> On Jul 11, 2018, at 2:19 PM, Trond Myklebust <trondmy@hammerspace.com> wrote:
> 
> On Wed, 2018-07-11 at 14:06 -0400, Chuck Lever wrote:
>>> On Jul 11, 2018, at 12:38 PM, Trond Myklebust <trondmy@hammerspace.
>>> com> wrote:
>>> 
>>> On Wed, 2018-07-11 at 12:05 -0400, Steve Dickson wrote:
>>>> Hey Trond,
>>>> 
>>>> On 07/11/2018 11:25 AM, Steve Dickson wrote:
>>>>> The cause is that the xdr_putlong uses a long to store the
>>>>> converted value, then passes it to fwrite as a byte buffer.
>>>>> Only the first 4 bytes are written, which is okay for a LE
>>>>> system after byteswapping, but writes all zeroes on BE systems.
>>>>> 
>>>>> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738
>>>>> 
>>>>> Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
>>>>> Signed-off-by: Steve Dickson <steved@redhat.com>
>>>>> ---
>>>>> v4: Use UINT32_MAX instead of INT32_MAX in boundary check.
>>>> 
>>>> Talking with some old crusty types ;-) they pointed out
>>>> that all these routines use a signed arguments and
>>>> always have... So again why is using an unsigned max
>>>> the right thing to do? 
>>> 
>>> As I said earlier, you are casting from a larger type to a smaller
>>> type, and you want it to work for both signed and unsigned 32-bit
>>> values. Consider this kind of code:
>>> 
>>>       int32_t foo = 0xFFFF0000;
>>>       ret = xdrstdio_putlong(xdr, foo);

I doubt that will compile everywhere, since the second parameter
is supposed to be a pointer. Even if we add "&" the C compiler
will likely not allow an implicit typecast and an "address of".

Let's call the API portably:

     long foo = 0xFFFF0000;
     ret = xdrstdio_putlong(xdr, &foo);

On a system with 32-bit longs, foo contains a negative value.

On a system with 64-bit longs, foo contains a positive value. My
narrow range check will fail, but a UINT32_MAX check would allow
xdrstdio_putlong to proceed.

My desired outcome is that the API works for the same range of
values on platforms with 32-bit longs and 64-bit longs. If this
API is to work the same on both classes of platform, I guess we
do want "*lp > UINT32_MAX || *lp < INT32_MIN".


>>> Since foo is signed, then (long)foo ends up getting cast to
>>> 0xFFFFFFFFFFFF0000L, which is negative, but is > (long)INT32_MIN.
>>> So
>>> ret == TRUE;


>> On 32-bit systems, xdrstdio_putlong() cannot work for values
>> between INT32_MAX and UINT32_MAX. It should return FALSE for
>> these values on 64-bit systems. In fact, that is the way this
>> API behaves for other 64-bit aware libtirpc implementations.
> 
> On a 32-bit system there is no need to check anything, because
> sizeof(long) == sizeof(int) == 4.

> The problems occur once you start casting from a smaller sized integer
> to a larger one because the unsigned cast will behave differently to
> the signed cast and result in a bitwise very different value.

I'm confused. The patch _removes_ unsigned typecasts. We're no
longer converting between signed and unsigned integers in these
two API functions.

xdrstdio_putlong converts a (potentially) larger signed integer
to a (potentially) smaller signed integer. If a larger integer
cannot fit in a smaller destination, the only thing that can
happen is that the most-significant bits of the larger integer
are discarded, IIUC.


>>> Now try:
>>> 
>>>       uint32_t bar = 0xFFFF0000U;
>>>       ret = xdrstdio_putlong(xdr, bar);
>>> 
>>> 
>>> Since bar is unsigned, then (long)bar gets cast to 0xFFFF0000L.
>>> That is
>>> clearly > (long)INT32_MAX == 0x7FFFFFFFL, and so the above fails
>>> with
>>> ret == FALSE.
>>> 
>>> 
>>> BTW: The above is pretty much exactly how xdr_int32_t() and
>>> xdr_uint32_t() work. The former does a signed cast to long, while
>>> the
>>> latter does an unsigned cast to long.
>> 
>> If that's the case, we should examine how other 64-bit aware
>> libtirpc implementations work and fix ours to behave the same.
>> Our libtirpc forked in the late 1990s before 64-bit systems
>> were widely deployed, so I have some doubts whether our
>> implementation is correct.
> 
> Observe:
> 
> bool_t
> xdr_int32_t(xdrs, int32_p)
>        XDR *xdrs;
>        int32_t *int32_p;
> {
>        long l;
> 
>        switch (xdrs->x_op) {
> 
>        case XDR_ENCODE:
>                l = (long) *int32_p;
>                return (XDR_PUTLONG(xdrs, &l));
> 
>        case XDR_DECODE:
>                if (!XDR_GETLONG(xdrs, &l)) {
>                        return (FALSE);
>                }
>                *int32_p = (int32_t) l;
>                return (TRUE);
> 
>        case XDR_FREE:
>                return (TRUE);
>        }
>        /* NOTREACHED */
>        return (FALSE);
> }
> 
> bool_t
> xdr_u_int32_t(xdrs, u_int32_p)
>        XDR *xdrs;
>        u_int32_t *u_int32_p;
> {
>        u_long l;
> 
>        switch (xdrs->x_op) {
> 
>        case XDR_ENCODE:
>                l = (u_long) *u_int32_p;
>                return (XDR_PUTLONG(xdrs, (long *)&l));
> 
>        case XDR_DECODE:
>                if (!XDR_GETLONG(xdrs, (long *)&l)) {
>                        return (FALSE);
>                }
>                *u_int32_p = (u_int32_t) l;
>                return (TRUE);
> 
>        case XDR_FREE:
>                return (TRUE);
>        }
>        /* NOTREACHED */
>        return (FALSE);
> }
> 
>>>> steved.
>>>> 
>>>>> 
>>>>> v3: Reworked the bounds checking
>>>>> 
>>>>> v2: Added bounds checking
>>>>>   Changed from unsigned to signed
>>>>> 
>>>>> src/xdr_stdio.c | 15 ++++++++++++---
>>>>> 1 file changed, 12 insertions(+), 3 deletions(-)
>>>>> 
>>>>> diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c
>>>>> index 4410262..846c7bf 100644
>>>>> --- a/src/xdr_stdio.c
>>>>> +++ b/src/xdr_stdio.c
>>>>> @@ -38,6 +38,7 @@
>>>>> */
>>>>> 
>>>>> #include <stdio.h>
>>>>> +#include <stdint.h>
>>>>> 
>>>>> #include <arpa/inet.h>
>>>>> #include <rpc/types.h>
>>>>> @@ -103,10 +104,12 @@ xdrstdio_getlong(xdrs, lp)
>>>>> 	XDR *xdrs;
>>>>> 	long *lp;
>>>>> {
>>>>> +	int32_t mycopy;
>>>>> 
>>>>> -	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs-
>>>>>> x_private) 
>>>>> != 1)
>>>>> +	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-
>>>>>> x_private) != 1)
>>>>> 
>>>>> 		return (FALSE);
>>>>> -	*lp = (long)ntohl((u_int32_t)*lp);
>>>>> +
>>>>> +	*lp = (long)ntohl(mycopy);
>>>>> 	return (TRUE);
>>>>> }
>>>>> 
>>>>> @@ -115,8 +118,14 @@ xdrstdio_putlong(xdrs, lp)
>>>>> 	XDR *xdrs;
>>>>> 	const long *lp;
>>>>> {
>>>>> -	long mycopy = (long)htonl((u_int32_t)*lp);
>>>>> +	int32_t mycopy;
>>>>> +
>>>>> +#if defined(_LP64)
>>>>> +	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))
>>>>> +		return (FALSE);
>>>>> +#endif
>>>>> 
>>>>> +	mycopy = (int32_t)htonl((int32_t)*lp);
>>>>> 	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs-
>>>>>> x_private) != 1)
>>>>> 
>>>>> 		return (FALSE);
>>>>> 	return (TRUE);
>>>>> 
>>>> 
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-
>>>> nfs"
>>>> in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.htm
>>>> l
>>> 
>>> -- 
>>> Trond Myklebust
>>> Linux NFS client maintainer, Hammerspace
>>> trond.myklebust@hammerspace.com
>>> 
>>> -----------------------------------------------------------------
>>> -------------
>>> Check out the vibrant tech community on one of the world's most
>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>> _______________________________________________
>>> Libtirpc-devel mailing list
>>> Libtirpc-devel@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/libtirpc-devel
>> 
>> --
>> Chuck Lever
>> 
>> 
>> 
> -- 
> Trond Myklebust
> CTO, Hammerspace Inc
> 4300 El Camino Real, Suite 105
> Los Altos, CA 94022
> www.hammer.space

--
Chuck Lever



--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
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More majordomo info at  http://vger.kernel.org/majordomo-info.html
Trond Myklebust July 11, 2018, 8:58 p.m. UTC | #6
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Steve Dickson July 18, 2018, 6:32 p.m. UTC | #7
On 07/11/2018 11:25 AM, Steve Dickson wrote:
> The cause is that the xdr_putlong uses a long to store the
> converted value, then passes it to fwrite as a byte buffer.
> Only the first 4 bytes are written, which is okay for a LE
> system after byteswapping, but writes all zeroes on BE systems.
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1261738
> 
> Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
> Signed-off-by: Steve Dickson <steved@redhat.com>
> ---
> v4: Use UINT32_MAX instead of INT32_MAX in boundary check.
> 
> v3: Reworked the bounds checking
> 
> v2: Added bounds checking
>     Changed from unsigned to signed
> 
>  src/xdr_stdio.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
Committed... 

steved.
> 
> diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c
> index 4410262..846c7bf 100644
> --- a/src/xdr_stdio.c
> +++ b/src/xdr_stdio.c
> @@ -38,6 +38,7 @@
>   */
>  
>  #include <stdio.h>
> +#include <stdint.h>
>  
>  #include <arpa/inet.h>
>  #include <rpc/types.h>
> @@ -103,10 +104,12 @@ xdrstdio_getlong(xdrs, lp)
>  	XDR *xdrs;
>  	long *lp;
>  {
> +	int32_t mycopy;
>  
> -	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
> +	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
>  		return (FALSE);
> -	*lp = (long)ntohl((u_int32_t)*lp);
> +
> +	*lp = (long)ntohl(mycopy);
>  	return (TRUE);
>  }
>  
> @@ -115,8 +118,14 @@ xdrstdio_putlong(xdrs, lp)
>  	XDR *xdrs;
>  	const long *lp;
>  {
> -	long mycopy = (long)htonl((u_int32_t)*lp);
> +	int32_t mycopy;
> +
> +#if defined(_LP64)
> +	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))
> +		return (FALSE);
> +#endif
>  
> +	mycopy = (int32_t)htonl((int32_t)*lp);
>  	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
>  		return (FALSE);
>  	return (TRUE);
> 
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Marc Eshel July 23, 2018, 6:43 p.m. UTC | #8
Hi Bruce,
Do you know of any plans to add  IETF RFC 8276 - File System Extended 
Attributes in NFSv4 to the Linux NFS Client or Server?
Marc.

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Marc Eshel July 23, 2018, 6:45 p.m. UTC | #9
Hi Bruce,
Do you know of any plans to add  IETF RFC 8276 - File System Extended 
Attributes in NFSv4 to the Linux NFS Client or Server?
Marc.



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J. Bruce Fields July 23, 2018, 8:33 p.m. UTC | #10
On Mon, Jul 23, 2018 at 11:43:55AM -0700, Marc Eshel wrote:
> Do you know of any plans to add  IETF RFC 8276 - File System Extended 
> Attributes in NFSv4 to the Linux NFS Client or Server?

I don't understand why you proposed new protocol without having anyone
in mind to implement it on the platforms where you need it.

Matt Benjamin's expressed interest in the past, but he's got a lot on
his plate so I don't know that we can count on that.

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diff mbox

Patch

diff --git a/src/xdr_stdio.c b/src/xdr_stdio.c
index 4410262..846c7bf 100644
--- a/src/xdr_stdio.c
+++ b/src/xdr_stdio.c
@@ -38,6 +38,7 @@ 
  */
 
 #include <stdio.h>
+#include <stdint.h>
 
 #include <arpa/inet.h>
 #include <rpc/types.h>
@@ -103,10 +104,12 @@  xdrstdio_getlong(xdrs, lp)
 	XDR *xdrs;
 	long *lp;
 {
+	int32_t mycopy;
 
-	if (fread(lp, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
+	if (fread(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
 		return (FALSE);
-	*lp = (long)ntohl((u_int32_t)*lp);
+
+	*lp = (long)ntohl(mycopy);
 	return (TRUE);
 }
 
@@ -115,8 +118,14 @@  xdrstdio_putlong(xdrs, lp)
 	XDR *xdrs;
 	const long *lp;
 {
-	long mycopy = (long)htonl((u_int32_t)*lp);
+	int32_t mycopy;
+
+#if defined(_LP64)
+	if ((*lp > UINT32_MAX) || (*lp < INT32_MIN))
+		return (FALSE);
+#endif
 
+	mycopy = (int32_t)htonl((int32_t)*lp);
 	if (fwrite(&mycopy, sizeof(int32_t), 1, (FILE *)xdrs->x_private) != 1)
 		return (FALSE);
 	return (TRUE);