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    SubjectRe: [PATCH] net: dsa: fix negative loop bound error on for loop
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    On 3/31/2019 8:03 PM, Andrew Lunn wrote:
    > On Sun, Mar 31, 2019 at 03:25:47PM +0530, Mukesh Ojha wrote:
    >> On 3/31/2019 3:12 AM, Colin King wrote:
    >>> From: Colin Ian King <colin.king@canonical.com>
    >>>
    >>> Currently the for-loop using an unsigned int for the loop counter
    >>> which is problematic when comparing it to the signed int count
    >>> This is an issue because if the signed int is negative then
    >>> the negative loop bound is implicitly cast to an unsigned int on
    >>> the comparison to loop counter i and will yield a very large value,
    >>> eventually causing an error when memmove/memcpy'ing outside the
    >>> allocated region pointed to by ndata.
    >>>
    >>> Fix this by simply making the loop counter i a signed int;
    >>>
    >>> Fixes: f2f2356685bc ("net: dsa: move master ethtool code")
    >>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
    >>> ---
    >>> net/dsa/master.c | 3 +--
    >>> 1 file changed, 1 insertion(+), 2 deletions(-)
    >>>
    >>> diff --git a/net/dsa/master.c b/net/dsa/master.c
    >>> index c58f33931be1..1b659647a303 100644
    >>> --- a/net/dsa/master.c
    >>> +++ b/net/dsa/master.c
    >>> @@ -87,8 +87,7 @@ static void dsa_master_get_strings(struct net_device *dev, uint32_t stringset,
    >>> struct dsa_switch *ds = cpu_dp->ds;
    >>> int port = cpu_dp->index;
    >>> int len = ETH_GSTRING_LEN;
    >>> - int mcount = 0, count;
    >>> - unsigned int i;
    >>> + int mcount = 0, count, i;
    >> This looks fine but why the return value checking for the negative will not
    >> be good here ?
    >>  count = ds->ops->get_sset_count(ds, port, stringset);
    > Hi Mukesh
    >
    > Is there a return value check for negative?


    Just checked looks like dsa_master_get_sset_count can never return -ve
    value .

    Colin,

    do we really get this situation in any scenario ?


    Thanks.

    Mukesh

    Mukesh

    >
    > Andrew

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