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netfilter: x_tables: check standard target size too
We have targets and standard targets -- the latter carries a verdict. The ip/ip6tables validation functions will access t->verdict for the standard targets to fetch the jump offset or verdict for chainloop detection, but this happens before the targets get checked/validated. Thus we also need to check for verdict presence here, else t->verdict can point right after a blob. Spotted with UBSAN while testing malformed blobs. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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@ -540,6 +540,13 @@ int xt_compat_match_to_user(const struct xt_entry_match *m,
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}
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EXPORT_SYMBOL_GPL(xt_compat_match_to_user);
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/* non-compat version may have padding after verdict */
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struct compat_xt_standard_target {
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struct compat_xt_entry_target t;
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compat_uint_t verdict;
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};
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/* see xt_check_entry_offsets */
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int xt_compat_check_entry_offsets(const void *base,
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unsigned int target_offset,
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unsigned int next_offset)
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@ -557,6 +564,10 @@ int xt_compat_check_entry_offsets(const void *base,
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if (target_offset + t->u.target_size > next_offset)
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return -EINVAL;
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if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&
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target_offset + sizeof(struct compat_xt_standard_target) != next_offset)
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return -EINVAL;
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return 0;
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}
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EXPORT_SYMBOL(xt_compat_check_entry_offsets);
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@ -596,6 +607,10 @@ int xt_check_entry_offsets(const void *base,
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if (target_offset + t->u.target_size > next_offset)
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return -EINVAL;
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if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&
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target_offset + sizeof(struct xt_standard_target) != next_offset)
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return -EINVAL;
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return 0;
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}
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EXPORT_SYMBOL(xt_check_entry_offsets);
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