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    Subject[PATCH 3.14 50/77] fs: nfsd: Fix signedness bug in compare_blob
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Rasmus Villemoes <linux@rasmusvillemoes.dk>

    commit ef17af2a817db97d42dd2ec0a425231748e23dbc upstream.

    Bugs similar to the one in acbbe6fbb240 (kcmp: fix standard comparison
    bug) are in rich supply.

    In this variant, the problem is that struct xdr_netobj::len has type
    unsigned int, so the expression o1->len - o2->len _also_ has type
    unsigned int; it has completely well-defined semantics, and the result
    is some non-negative integer, which is always representable in a long
    long. But this means that if the conditional triggers, we are
    guaranteed to return a positive value from compare_blob.

    In this case it could be fixed by

    - res = o1->len - o2->len;
    + res = (long long)o1->len - (long long)o2->len;

    but I'd rather eliminate the usually broken 'return a - b;' idiom.

    Reviewed-by: Jeff Layton <jlayton@primarydata.com>
    Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfsd/nfs4state.c | 15 +++++++--------
    1 file changed, 7 insertions(+), 8 deletions(-)

    --- a/fs/nfsd/nfs4state.c
    +++ b/fs/nfsd/nfs4state.c
    @@ -1209,15 +1209,14 @@ static int copy_cred(struct svc_cred *ta
    return 0;
    }

    -static long long
    +static int
    compare_blob(const struct xdr_netobj *o1, const struct xdr_netobj *o2)
    {
    - long long res;
    -
    - res = o1->len - o2->len;
    - if (res)
    - return res;
    - return (long long)memcmp(o1->data, o2->data, o1->len);
    + if (o1->len < o2->len)
    + return -1;
    + if (o1->len > o2->len)
    + return 1;
    + return memcmp(o1->data, o2->data, o1->len);
    }

    static int same_name(const char *n1, const char *n2)
    @@ -1401,7 +1400,7 @@ add_clp_to_name_tree(struct nfs4_client
    static struct nfs4_client *
    find_clp_in_name_tree(struct xdr_netobj *name, struct rb_root *root)
    {
    - long long cmp;
    + int cmp;
    struct rb_node *node = root->rb_node;
    struct nfs4_client *clp;




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