Commit fc788f64 authored Aug 18, 2017 by Chuck Lever Committed by J. Bruce Fields Aug 24, 2017

nfsd: Limit end of page list when decoding NFSv4 WRITE



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.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent eff79368

fs/nfsd/nfs4xdr.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -144,7 +144,7 @@ static void next_decode_page(struct nfsd4_compoundargs *argp)
		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_compoundargs argp, struct nfsd4_write write)
		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);

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