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linux/drivers/net/ppp
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Guillaume Nault 6ec6ec3bbb ppp: fix xmit recursion detection on ppp channels 
[ Upstream commit 0a0e1a85c8 ]

Commit e5dadc65f9 ("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: e5dadc65f9 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2017-08-12 19:31:21 -07:00
..
bsd_comp.c ppp: Move the PPP drivers 2011-08-27 00:58:26 -07:00
Kconfig tty/serial patches for 3.9-rc1 2013-02-21 13:41:04 -08:00
Makefile ppp: Move the PPP drivers 2011-08-27 00:58:26 -07:00
ppp_async.c tty: Fix recursive deadlock in tty_perform_flush() 2013-03-18 16:52:24 -07:00
ppp_deflate.c ppp: deflate: never return len larger than output buffer 2015-01-29 14:50:01 -08:00
ppp_generic.c ppp: fix xmit recursion detection on ppp channels 2017-08-12 19:31:21 -07:00
ppp_mppe.c ppp_mppe: Use skcipher and ahash 2016-01-27 20:35:45 +08:00
ppp_mppe.h ppp: Move the PPP drivers 2011-08-27 00:58:26 -07:00
ppp_synctty.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-05-01 14:08:52 -07:00
pppoe.c pppoe: fix reference counting in PPPoE proxy 2016-02-17 16:02:01 -05:00
pppox.c pppox: use standard module auto-loading feature 2015-12-03 15:12:54 -05:00
pptp.c pptp: Refactor the struct and macros of PPTP codes 2016-08-15 10:55:53 -07:00