[PATCH v2] SUNRPC: Fix READ_PLUS crasher

[PATCH v2] SUNRPC: Fix READ_PLUS crasher

[Chuck Lever]

Looks like there are still cases when "space_left - frag1bytes" can
legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains
within the current encode buffer.

Reported-by: Bruce Fields <bfields@fieldses.org>
Reported-by: Zorro Lang <zlang@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151
Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xdr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index f87a2d8f23a7..5d2b3e6979fb 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -984,7 +984,7 @@ static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 	p = page_address(*xdr->page_ptr);
 	xdr->p = p + frag2bytes;
 	space_left = xdr->buf->buflen - xdr->buf->len;
-	if (space_left - nbytes >= PAGE_SIZE)
+	if (space_left - frag1bytes >= PAGE_SIZE)
 		xdr->end = p + PAGE_SIZE;
 	else
 		xdr->end = p + space_left - frag1bytes;

Re: [PATCH v2] SUNRPC: Fix READ_PLUS crasher

[J. Bruce Fields]

This also gets through my tests without a crash.--b.

On Thu, Jun 30, 2022 at 04:48:18PM -0400, Chuck Lever wrote:
> Looks like there are still cases when "space_left - frag1bytes" can
> legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains
> within the current encode buffer.
> 
> Reported-by: Bruce Fields <bfields@fieldses.org>
> Reported-by: Zorro Lang <zlang@redhat.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151
> Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()")
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  net/sunrpc/xdr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> index f87a2d8f23a7..5d2b3e6979fb 100644
> --- a/net/sunrpc/xdr.c
> +++ b/net/sunrpc/xdr.c
> @@ -984,7 +984,7 @@ static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
>  	p = page_address(*xdr->page_ptr);
>  	xdr->p = p + frag2bytes;
>  	space_left = xdr->buf->buflen - xdr->buf->len;
> -	if (space_left - nbytes >= PAGE_SIZE)
> +	if (space_left - frag1bytes >= PAGE_SIZE)
>  		xdr->end = p + PAGE_SIZE;
>  	else
>  		xdr->end = p + space_left - frag1bytes;
> 

Re: [PATCH v2] SUNRPC: Fix READ_PLUS crasher

[Zorro Lang]

On Thu, Jun 30, 2022 at 04:48:18PM -0400, Chuck Lever wrote:
> Looks like there are still cases when "space_left - frag1bytes" can
> legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains
> within the current encode buffer.
> 
> Reported-by: Bruce Fields <bfields@fieldses.org>
> Reported-by: Zorro Lang <zlang@redhat.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151
> Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()")
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---

I can't reproduce this bug by merging this patch:

FSTYP         -- nfs
PLATFORM      -- Linux/x86_64 ibm-xxxxx-08 5.19.0-rc4+ #1 SMP PREEMPT_DYNAMIC Sat Jul 2 09:59:50 EDT 2022
MKFS_OPTIONS  -- ibm-xxxxx-xx.xxx.xxx.xxx.xxxxxx.com:/mnt/xfstests/scratch/nfs-server
MOUNT_OPTIONS -- -o vers=4.2 -o context=system_u:object_r:root_t:s0 ibm-x3650m4-08.rhts.eng.pek2.redhat.com:/mnt/xfstests/scratch/nfs-server /mnt/xfstests/scratch/nfs-client

generic/465        12s
Ran: generic/465
Passed all 1 tests

>  net/sunrpc/xdr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> index f87a2d8f23a7..5d2b3e6979fb 100644
> --- a/net/sunrpc/xdr.c
> +++ b/net/sunrpc/xdr.c
> @@ -984,7 +984,7 @@ static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
>  	p = page_address(*xdr->page_ptr);
>  	xdr->p = p + frag2bytes;
>  	space_left = xdr->buf->buflen - xdr->buf->len;
> -	if (space_left - nbytes >= PAGE_SIZE)
> +	if (space_left - frag1bytes >= PAGE_SIZE)
>  		xdr->end = p + PAGE_SIZE;
>  	else
>  		xdr->end = p + space_left - frag1bytes;
> 
> 

Re: [PATCH v2] SUNRPC: Fix READ_PLUS crasher

[Chuck Lever III]

> On Jul 4, 2022, at 2:55 AM, Zorro Lang <zlang@redhat.com> wrote:
> 
> On Thu, Jun 30, 2022 at 04:48:18PM -0400, Chuck Lever wrote:
>> Looks like there are still cases when "space_left - frag1bytes" can
>> legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains
>> within the current encode buffer.
>> 
>> Reported-by: Bruce Fields <bfields@fieldses.org>
>> Reported-by: Zorro Lang <zlang@redhat.com>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151
>> Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()")
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
> 
> I can't reproduce this bug by merging this patch:
> 
> FSTYP         -- nfs
> PLATFORM      -- Linux/x86_64 ibm-xxxxx-08 5.19.0-rc4+ #1 SMP PREEMPT_DYNAMIC Sat Jul 2 09:59:50 EDT 2022
> MKFS_OPTIONS  -- ibm-xxxxx-xx.xxx.xxx.xxx.xxxxxx.com:/mnt/xfstests/scratch/nfs-server
> MOUNT_OPTIONS -- -o vers=4.2 -o context=system_u:object_r:root_t:s0 ibm-x3650m4-08.rhts.eng.pek2.redhat.com:/mnt/xfstests/scratch/nfs-server /mnt/xfstests/scratch/nfs-client
> 
> generic/465        12s
> Ran: generic/465
> Passed all 1 tests

Thanks for testing!


>> net/sunrpc/xdr.c |    2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
>> index f87a2d8f23a7..5d2b3e6979fb 100644
>> --- a/net/sunrpc/xdr.c
>> +++ b/net/sunrpc/xdr.c
>> @@ -984,7 +984,7 @@ static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
>> 	p = page_address(*xdr->page_ptr);
>> 	xdr->p = p + frag2bytes;
>> 	space_left = xdr->buf->buflen - xdr->buf->len;
>> -	if (space_left - nbytes >= PAGE_SIZE)
>> +	if (space_left - frag1bytes >= PAGE_SIZE)
>> 		xdr->end = p + PAGE_SIZE;
>> 	else
>> 		xdr->end = p + space_left - frag1bytes;
>> 
>> 
> 

--
Chuck Lever