Patch "nfsd: Limit end of page list when decoding NFSv4 WRITE" has been added to the 4.12-stable tree

This is a note to let you know that I've just added the patch titled

nfsd: Limit end of page list when decoding NFSv4 WRITE

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nfsd-limit-end-of-page-list-when-decoding-nfsv4-write.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Chuck Lever <[email protected]>
Date: Fri, 18 Aug 2017 11:12:19 -0400
Subject: nfsd: Limit end of page list when decoding NFSv4 WRITE

From: Chuck Lever <[email protected]>

commit fc788f64f1f3eb31e87d4f53bcf1ab76590d5838 upstream.

When processing an NFSv4 WRITE operation, argp->end should never point past the end of the data in the final page of the page list. Otherwise, nfsd4_decode_compound can walk into uninitialized memory.

More critical, nfsd4_decode_write is failing to increment argp->pagelen when it increments argp->pagelist. This can cause later xdr decoders to assume more data is available than really is, which can cause server crashes on malformed requests.

---
 fs/nfsd/nfs4xdr.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

@@ -144,7 +144,7 @@ static void next_decode_page(struct nfsd
 	argp->p = page_address(argp->pagelist[0]);
 	argp->pagelist++;
 	if (argp->pagelen < PAGE_SIZE) {
-		argp->end = argp->p + (argp->pagelen>>2);
+		argp->end = argp->p + XDR_QUADLEN(argp->pagelen);
 		argp->pagelen = 0;
 	} else {
 		argp->end = argp->p + (PAGE_SIZE>>2);

@@ -1279,9 +1279,7 @@ nfsd4_decode_write(struct nfsd4_compound
 		argp->pagelen -= pages * PAGE_SIZE;
 		len -= pages * PAGE_SIZE;
 
-		argp->p = (__be32 *)page_address(argp->pagelist[0]);
-		argp->pagelist++;
-		argp->end = argp->p + XDR_QUADLEN(PAGE_SIZE);
+		next_decode_page(argp);
 	}
 	argp->p += XDR_QUADLEN(len);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/nfsd-limit-end-of-page-list-when-decoding-nfsv4-write.patch