Commit 599be01e authored by Cong Wang's avatar Cong Wang Committed by David S. Miller
Browse files

net_sched: fix an OOB access in cls_tcindex 



As Eric noticed, tcindex_alloc_perfect_hash() uses cp->hash
to compute the size of memory allocation, but cp->hash is
set again after the allocation, this caused an out-of-bound
access.

So we have to move all cp->hash initialization and computation
before the memory allocation. Move cp->mask and cp->shift together
as cp->hash may need them for computation too.

Reported-and-tested-by: default avatar <syzbot+35d4dea36c387813ed31@syzkaller.appspotmail.com>
Fixes: 331b7292 ("net: sched: RCU cls_tcindex")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 83b43045

net/sched/cls_tcindex.c

+20 −20
Original line number Diff line number Diff line
@@ -333,12 +333,31 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	cp->fall_through = p->fall_through;

	cp->tp = tp;



	if (tb[TCA_TCINDEX_HASH])

		cp->hash = nla_get_u32(tb[TCA_TCINDEX_HASH]);



	if (tb[TCA_TCINDEX_MASK])

		cp->mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);



	if (tb[TCA_TCINDEX_SHIFT])

		cp->shift = nla_get_u32(tb[TCA_TCINDEX_SHIFT]);



	if (!cp->hash) {

		/* Hash not specified, use perfect hash if the upper limit

		 * of the hashing index is below the threshold.

		 */

		if ((cp->mask >> cp->shift) < PERFECT_HASH_THRESHOLD)

			cp->hash = (cp->mask >> cp->shift) + 1;

		else

			cp->hash = DEFAULT_HASH_SIZE;

	}



	if (p->perfect) {

		int i;



		if (tcindex_alloc_perfect_hash(net, cp) < 0)

			goto errout;

		for (i = 0; i < cp->hash; i++)

		for (i = 0; i < min(cp->hash, p->hash); i++)

			cp->perfect[i].res = p->perfect[i].res;

		balloc = 1;

	}
@@ -350,15 +369,6 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	if (old_r)

		cr = r->res;



	if (tb[TCA_TCINDEX_HASH])

		cp->hash = nla_get_u32(tb[TCA_TCINDEX_HASH]);



	if (tb[TCA_TCINDEX_MASK])

		cp->mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);



	if (tb[TCA_TCINDEX_SHIFT])

		cp->shift = nla_get_u32(tb[TCA_TCINDEX_SHIFT]);



	err = -EBUSY;



	/* Hash already allocated, make sure that we still meet the
@@ -376,16 +386,6 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	if (tb[TCA_TCINDEX_FALL_THROUGH])

		cp->fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);



	if (!cp->hash) {

		/* Hash not specified, use perfect hash if the upper limit

		 * of the hashing index is below the threshold.

		 */

		if ((cp->mask >> cp->shift) < PERFECT_HASH_THRESHOLD)

			cp->hash = (cp->mask >> cp->shift) + 1;

		else

			cp->hash = DEFAULT_HASH_SIZE;

	}



	if (!cp->perfect && !cp->h)

		cp->alloc_hash = cp->hash;

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