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    Subject[PATCH 3.16 137/294] nfsd: Limit end of page list when decoding NFSv4 WRITE
    3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Chuck Lever <chuck.lever@oracle.com>

    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.

    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    fs/nfsd/nfs4xdr.c | 6 ++----
    1 file changed, 2 insertions(+), 4 deletions(-)

    --- a/fs/nfsd/nfs4xdr.c
    +++ b/fs/nfsd/nfs4xdr.c
    @@ -134,7 +134,7 @@ 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);
    @@ -1246,9 +1246,7 @@ 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);

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