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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: syzbot+35d4dea36c387813ed31@syzkaller.appspotmail.com
Fixes: 331b72922c ("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: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Cong Wang 2020-02-02 21:14:35 -08:00 committed by David S. Miller
parent 83b4304530
commit 599be01ee5
1 changed files with 20 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
net/sched/cls_tcindex.c
View File

@ -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;