path: root/drivers/net/ppp
diff options
authorGuillaume Nault <g.nault@alphalink.fr>2017-08-08 11:43:24 +0200
committerDavid S. Miller <davem@davemloft.net>2017-08-08 21:06:11 -0700
commit0a0e1a85c83775a648041be2b15de6d0a2f2b8eb (patch)
treefc0213c8398f647311a6f3e1abaafd1670196a89 /drivers/net/ppp
parentrds: Reintroduce statistics counting (diff)
ppp: fix xmit recursion detection on ppp channels
Commit e5dadc65f9e0 ("ppp: Fix false xmit recursion detect with two ppp devices") dropped the xmit_recursion counter incrementation in ppp_channel_push() and relied on ppp_xmit_process() for this task. But __ppp_channel_push() can also send packets directly (using the .start_xmit() channel callback), in which case the xmit_recursion counter isn't incremented anymore. If such packets get routed back to the parent ppp unit, ppp_xmit_process() won't notice the recursion and will call ppp_channel_push() on the same channel, effectively creating the deadlock situation that the xmit_recursion mechanism was supposed to prevent. This patch re-introduces the xmit_recursion counter incrementation in ppp_channel_push(). Since the xmit_recursion variable is now part of the parent ppp unit, incrementation is skipped if the channel doesn't have any. This is fine because only packets routed through the parent unit may enter the channel recursively. Finally, we have to ensure that pch->ppp is not going to be modified while executing ppp_channel_push(). Instead of taking this lock only while calling ppp_xmit_process(), we now have to hold it for the full ppp_channel_push() execution. This respects the ppp locks ordering which requires locking ->upl before ->downl. Fixes: e5dadc65f9e0 ("ppp: Fix false xmit recursion detect with two ppp devices") Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ppp')
1 files changed, 10 insertions, 8 deletions
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index bd4303944e44..a404552555d4 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1915,21 +1915,23 @@ static void __ppp_channel_push(struct channel *pch)
/* see if there is anything from the attached unit to be sent */
if (skb_queue_empty(&pch->file.xq)) {
- read_lock(&pch->upl);
ppp = pch->ppp;
if (ppp)
- ppp_xmit_process(ppp);
- read_unlock(&pch->upl);
+ __ppp_xmit_process(ppp);
static void ppp_channel_push(struct channel *pch)
- local_bh_disable();
- __ppp_channel_push(pch);
- local_bh_enable();
+ read_lock_bh(&pch->upl);
+ if (pch->ppp) {
+ (*this_cpu_ptr(pch->ppp->xmit_recursion))++;
+ __ppp_channel_push(pch);
+ (*this_cpu_ptr(pch->ppp->xmit_recursion))--;
+ } else {
+ __ppp_channel_push(pch);
+ }
+ read_unlock_bh(&pch->upl);