diff options
| author | Eric Dumazet <eric.dumazet@gmail.com> | 2012-02-09 16:13:19 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-02-13 11:06:13 -0800 |
| commit | 8a533666d1591cf4ea596c6bd710e2fe682cb56a (patch) | |
| tree | 0c525703fd834499c659490b3cb38835fde14f51 /net/atm | |
| parent | 323a479328cbc2fb5cf647790f7414ca570a577b (diff) | |
net: fix NULL dereferences in check_peer_redir()
[ Upstream commit d3aaeb38c40e5a6c08dd31a1b64da65c4352be36, along
with dependent backports of commits:
69cce1d1404968f78b177a0314f5822d5afdbbfb
9de79c127cccecb11ae6a21ab1499e87aa222880
218fa90f072e4aeff9003d57e390857f4f35513e
580da35a31f91a594f3090b7a2c39b85cb051a12
f7e57044eeb1841847c24aa06766c8290c202583
e049f28883126c689cf95859480d9ee4ab23b7fa ]
Gergely Kalman reported crashes in check_peer_redir().
It appears commit f39925dbde778 (ipv4: Cache learned redirect
information in inetpeer.) added a race, leading to possible NULL ptr
dereference.
Since we can now change dst neighbour, we should make sure a reader can
safely use a neighbour.
Add RCU protection to dst neighbour, and make sure check_peer_redir()
can be called safely by different cpus in parallel.
As neighbours are already freed after one RCU grace period, this patch
should not add typical RCU penalty (cache cold effects)
Many thanks to Gergely for providing a pretty report pointing to the
bug.
Reported-by: Gergely Kalman <synapse@hippy.csoma.elte.hu>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/atm')
| -rw-r--r-- | net/atm/clip.c | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/net/atm/clip.c b/net/atm/clip.c index 1d4be60e139..5889074e971 100644 --- a/net/atm/clip.c +++ b/net/atm/clip.c @@ -364,33 +364,37 @@ static netdev_tx_t clip_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct clip_priv *clip_priv = PRIV(dev); + struct dst_entry *dst = skb_dst(skb); struct atmarp_entry *entry; + struct neighbour *n; struct atm_vcc *vcc; int old; unsigned long flags; pr_debug("(skb %p)\n", skb); - if (!skb_dst(skb)) { + if (!dst) { pr_err("skb_dst(skb) == NULL\n"); dev_kfree_skb(skb); dev->stats.tx_dropped++; return NETDEV_TX_OK; } - if (!skb_dst(skb)->neighbour) { + n = dst_get_neighbour(dst); + if (!n) { #if 0 - skb_dst(skb)->neighbour = clip_find_neighbour(skb_dst(skb), 1); - if (!skb_dst(skb)->neighbour) { + n = clip_find_neighbour(skb_dst(skb), 1); + if (!n) { dev_kfree_skb(skb); /* lost that one */ dev->stats.tx_dropped++; return 0; } + dst_set_neighbour(dst, n); #endif pr_err("NO NEIGHBOUR !\n"); dev_kfree_skb(skb); dev->stats.tx_dropped++; return NETDEV_TX_OK; } - entry = NEIGH2ENTRY(skb_dst(skb)->neighbour); + entry = NEIGH2ENTRY(n); if (!entry->vccs) { if (time_after(jiffies, entry->expires)) { /* should be resolved */ @@ -407,7 +411,7 @@ static netdev_tx_t clip_start_xmit(struct sk_buff *skb, } pr_debug("neigh %p, vccs %p\n", entry, entry->vccs); ATM_SKB(skb)->vcc = vcc = entry->vccs->vcc; - pr_debug("using neighbour %p, vcc %p\n", skb_dst(skb)->neighbour, vcc); + pr_debug("using neighbour %p, vcc %p\n", n, vcc); if (entry->vccs->encap) { void *here; |