| Message ID | 20180313053248.13654-2-jelsasser@appneta.com |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | net: avoid a kernel panic during sk_busy_loop | expand |
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: > > > 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 <jelsasser@appneta.com> > --- > 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>
From: Josh Elsasser <jelsasser@appneta.com> Date: Mon, 12 Mar 2018 22:32:00 -0700 > 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: ... > Commit 79e7fff47b7b ("net: remove support for per driver ndo_busy_poll()") > indirectly fixed this upstream in linux-4.11 by removing the offending > pointer usage. No other users of napi->dev touch its netdev_ops. > > 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 <jelsasser@appneta.com> Ok, queued up for -stable, thanks.
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;
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: BUG: unable to handle kernel NULL pointer dereference at 00000000000000c8 IP: [<ffffffff817b4b72>] sk_busy_loop+0x92/0x2f0 Call Trace: [<ffffffff815a3134>] ? uart_write_room+0x74/0xf0 [<ffffffff817964a9>] sock_poll+0x99/0xa0 [<ffffffff81223142>] do_sys_poll+0x2e2/0x520 [<ffffffff8118d3fc>] ? get_page_from_freelist+0x3bc/0xa30 [<ffffffff810ada22>] ? update_curr+0x62/0x140 [<ffffffff811ea671>] ? __slab_free+0xa1/0x2a0 [<ffffffff811ea671>] ? __slab_free+0xa1/0x2a0 [<ffffffff8179dbb1>] ? skb_free_head+0x21/0x30 [<ffffffff81221bd0>] ? poll_initwait+0x50/0x50 [<ffffffff811eaa36>] ? kmem_cache_free+0x1c6/0x1e0 [<ffffffff815a4884>] ? uart_write+0x124/0x1d0 [<ffffffff810bd1cd>] ? remove_wait_queue+0x4d/0x60 [<ffffffff810bd224>] ? __wake_up+0x44/0x50 [<ffffffff81582731>] ? tty_write_unlock+0x31/0x40 [<ffffffff8158c5c6>] ? tty_ldisc_deref+0x16/0x20 [<ffffffff81584820>] ? tty_write+0x1e0/0x2f0 [<ffffffff81587e50>] ? process_echoes+0x80/0x80 [<ffffffff8120c17b>] ? __vfs_write+0x2b/0x130 [<ffffffff8120d09a>] ? vfs_write+0x15a/0x1a0 [<ffffffff81223455>] SyS_poll+0x75/0x100 [<ffffffff819a6524>] entry_SYSCALL_64_fastpath+0x24/0xcf Commit 79e7fff47b7b ("net: remove support for per driver ndo_busy_poll()") indirectly fixed this upstream in linux-4.11 by removing the offending pointer usage. No other users of napi->dev touch its netdev_ops. 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 <jelsasser@appneta.com> --- net/core/dev.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)