netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets
We need to make sure the offsets are not out of range of the total size. Also check that they are in ascending order. The WARN_ON triggered by syzkaller (it sets panic_on_warn) is changed to also bail out, no point in continuing parsing. Briefly tested with simple ruleset of -A INPUT --limit 1/s' --log plus jump to custom chains using 32bit ebtables binary. Reported-by: <syzbot+845a53d13171abf8bf29@syzkaller.appspotmail.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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@ -2060,7 +2060,9 @@ static int ebt_size_mwt(struct compat_ebt_entry_mwt *match32,
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if (match_kern)
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match_kern->match_size = ret;
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WARN_ON(type == EBT_COMPAT_TARGET && size_left);
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if (WARN_ON(type == EBT_COMPAT_TARGET && size_left))
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return -EINVAL;
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match32 = (struct compat_ebt_entry_mwt *) buf;
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}
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@ -2116,6 +2118,15 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base,
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*
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* offsets are relative to beginning of struct ebt_entry (i.e., 0).
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*/
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for (i = 0; i < 4 ; ++i) {
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if (offsets[i] >= *total)
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return -EINVAL;
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if (i == 0)
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continue;
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if (offsets[i-1] > offsets[i])
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return -EINVAL;
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}
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for (i = 0, j = 1 ; j < 4 ; j++, i++) {
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struct compat_ebt_entry_mwt *match32;
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unsigned int size;
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