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netfilter: xt_u32: validate user space input

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The xt_u32 module doesn't validate the fields in the xt_u32 structure.
An attacker may take advantage of this to trigger an OOB read by setting
the size fields with a value beyond the arrays boundaries.

Add a checkentry function to validate the structure.

This was originally reported by the ZDI project (ZDI-CAN-18408).

Fixes: 1b50b8a371 ("[NETFILTER]: Add u32 match")
Cc: stable@vger.kernel.org
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Wander Lairson Costa 2023-08-28 10:21:07 -03:00 committed by Pablo Neira Ayuso
parent e994764976
commit 69c5d284f6
1 changed files with 21 additions and 0 deletions
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21
net/netfilter/xt_u32.c
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@ -96,11 +96,32 @@ static bool u32_mt(const struct sk_buff *skb, struct xt_action_param *par)
return ret ^ data->invert;
}
static int u32_mt_checkentry(const struct xt_mtchk_param *par)
{
const struct xt_u32 *data = par->matchinfo;
const struct xt_u32_test *ct;
unsigned int i;
if (data->ntests > ARRAY_SIZE(data->tests))
return -EINVAL;
for (i = 0; i < data->ntests; ++i) {
ct = &data->tests[i];
if (ct->nnums > ARRAY_SIZE(ct->location) ||
ct->nvalues > ARRAY_SIZE(ct->value))
return -EINVAL;
}
return 0;
}
static struct xt_match xt_u32_mt_reg __read_mostly = {
.name = "u32",
.revision = 0,
.family = NFPROTO_UNSPEC,
.match = u32_mt,
.checkentry = u32_mt_checkentry,
.matchsize = sizeof(struct xt_u32),
.me = THIS_MODULE,
};