Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit db856674 authored by Eric Dumazet's avatar Eric Dumazet Committed by Patrick McHardy
Browse files

netfilter: xtables: fix reentrancy 



commit f3c5c1bf (make ip_tables reentrant) introduced a race in
handling the stackptr restore, at the end of ipt_do_table()

We should do it before the call to xt_info_rdunlock_bh(), or we allow
cpu preemption and another cpu overwrites stackptr of original one.

A second fix is to change the underflow test to check the origptr value
instead of 0 to detect underflow, or else we allow a jump from different
hooks.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
parent 5c1aba46

net/ipv4/netfilter/ip_tables.c

+2 −2
Original line number Diff line number Diff line
@@ -387,7 +387,7 @@ ipt_do_table(struct sk_buff *skb, 
					verdict = (unsigned)(-v) - 1;

					break;

				}

				if (*stackptr == 0) {

				if (*stackptr <= origptr) {

					e = get_entry(table_base,

					    private->underflow[hook]);

					pr_debug("Underflow (this is normal) "
@@ -427,10 +427,10 @@ ipt_do_table(struct sk_buff *skb, 
			/* Verdict */

			break;

	} while (!acpar.hotdrop);

	xt_info_rdunlock_bh();

	pr_debug("Exiting %s; resetting sp from %u to %u\n",

		 __func__, *stackptr, origptr);

	*stackptr = origptr;

	xt_info_rdunlock_bh();

#ifdef DEBUG_ALLOW_ALL

	return NF_ACCEPT;

#else

net/ipv6/netfilter/ip6_tables.c

+2 −2
Original line number Diff line number Diff line
@@ -410,7 +410,7 @@ ip6t_do_table(struct sk_buff *skb, 
					verdict = (unsigned)(-v) - 1;

					break;

				}

				if (*stackptr == 0)

				if (*stackptr <= origptr)

					e = get_entry(table_base,

					    private->underflow[hook]);

				else
@@ -441,8 +441,8 @@ ip6t_do_table(struct sk_buff *skb, 
			break;

	} while (!acpar.hotdrop);



	xt_info_rdunlock_bh();

	*stackptr = origptr;

	xt_info_rdunlock_bh();



#ifdef DEBUG_ALLOW_ALL

	return NF_ACCEPT;