Re: [PATCH v2 1/1] net: check before dereferencing netdev_ops during busy poll
From: Eric Dumazet <hidden>
Date: 2018-03-13 05:50:54
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On 03/12/2018 10:32 PM, Josh Elsasser wrote:
init_dummy_netdev() leaves its netdev_ops pointer zeroed. This leads to a NULL pointer dereference when sk_busy_loop fires against an iwlwifi wireless adapter and checks napi->dev->netdev_ops->ndo_busy_poll. Avoid this by ensuring napi->dev->netdev_ops is valid before following the pointer, avoiding the following panic when busy polling on a dummy netdev:
quoted hunk ↗ jump to hunk
Fixes: 060212928670 ("net: add low latency socket poll") Fixes: ce6aea93f751 ("net: network drivers no longer need to implement ndo_busy_poll()") - 4.9.y Signed-off-by: Josh Elsasser <redacted> --- net/core/dev.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)diff --git a/net/core/dev.c b/net/core/dev.c index 8898618bf341..1f50c131ed15 100644 --- a/net/core/dev.c +++ b/net/core/dev.c@@ -5042,7 +5042,10 @@ bool sk_busy_loop(struct sock *sk, int nonblock) goto out; /* Note: ndo_busy_poll method is optional in linux-4.5 */ - busy_poll = napi->dev->netdev_ops->ndo_busy_poll; + if (napi->dev->netdev_ops) + busy_poll = napi->dev->netdev_ops->ndo_busy_poll; + else + busy_poll = NULL; do { rc = 0;
We could instead setup a non NULL netdev_ops pointer on these 'dummy' devices to not add a check in fast path, but I presume we do not really care since this fix is for old kernels, and considering how long it took to discover this bug. Reviewed-by: Eric Dumazet <edumazet@google.com>