From ca2a05aa7c72309ee65164c78fa2be7a5038215e Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Sun, 11 Nov 2007 15:43:12 -0500 Subject: [PATCH] nfsd: Fix handling of negative lengths in read_buf() The length "nbytes" passed into read_buf should never be negative, but we check only for too-large values of "nbytes", not for too-small values. Make nbytes unsigned, so it's clear that the former tests are sufficient. (Despite this read_buf() currently correctly returns an xdr error in the case of a negative length, thanks to an unsigned comparison with size_of() and bounds-checking in kmalloc(). This seems very fragile, though.) Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4xdr.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 57333944af..bf1e792a65 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -148,12 +148,12 @@ xdr_error: \ } \ } while (0) -static __be32 *read_buf(struct nfsd4_compoundargs *argp, int nbytes) +static __be32 *read_buf(struct nfsd4_compoundargs *argp, u32 nbytes) { /* We want more bytes than seem to be available. * Maybe we need a new page, maybe we have just run out */ - int avail = (char*)argp->end - (char*)argp->p; + unsigned int avail = (char *)argp->end - (char *)argp->p; __be32 *p; if (avail + argp->pagelen < nbytes) return NULL; @@ -169,6 +169,11 @@ static __be32 *read_buf(struct nfsd4_compoundargs *argp, int nbytes) return NULL; } + /* + * The following memcpy is safe because read_buf is always + * called with nbytes > avail, and the two cases above both + * guarantee p points to at least nbytes bytes. + */ memcpy(p, argp->p, avail); /* step to next page */ argp->p = page_address(argp->pagelist[0]); -- 2.20.1