Re: [PATCH 2/2] mlxsw: spectrum_router: avoid potential uninitialized data usage

From: Ido Schimmel
Date: Fri Sep 30 2016 - 14:03:30 EST

On Fri, Sep 30, 2016 at 06:17:10PM +0200, Arnd Bergmann wrote:
> If fi->fib_nhs is zero, the router interface pointer is uninitialized, as shown by
> this warning:
> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c: In function 'mlxsw_sp_router_fib_event':
> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:1674:21: error: 'r' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:1643:23: note: 'r' was declared here
> This changes the loop so we handle the case the same way as finding no router
> interface pointer attached to one of the nexthops to ensure we always
> trap here instead of using uninitialized data.
> Fixes: b45f64d16d45 ("mlxsw: spectrum_router: Use FIB notifications instead of switchdev calls")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

For net-next:
Acked-by: Ido Schimmel <idosch@xxxxxxxxxxxx>

BTW, which flags did you pass to generate this error? I can only
reproduce this with EXTRA_CFLAGS="-Wmaybe-uninitialized -Werror", but
for some reason EXTRA_CFLAGS="-Wall -Werror" is silent. Any idea why? I
would like to add this to my git hooks and avoid these errors in the
future :)