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Commit 7ed2abdd authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
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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: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent fc1221b3

net/netfilter/x_tables.c

+15 −0
Original line number Diff line number Diff line
@@ -540,6 +540,13 @@ int xt_compat_match_to_user(const struct xt_entry_match *m, 
}

EXPORT_SYMBOL_GPL(xt_compat_match_to_user);



/* non-compat version may have padding after verdict */

struct compat_xt_standard_target {

	struct compat_xt_entry_target t;

	compat_uint_t verdict;

};



/* see xt_check_entry_offsets */

int xt_compat_check_entry_offsets(const void *base,

				  unsigned int target_offset,

				  unsigned int next_offset)
@@ -557,6 +564,10 @@ int xt_compat_check_entry_offsets(const void *base, 
	if (target_offset + t->u.target_size > next_offset)

		return -EINVAL;



	if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&

	    target_offset + sizeof(struct compat_xt_standard_target) != next_offset)

		return -EINVAL;



	return 0;

}

EXPORT_SYMBOL(xt_compat_check_entry_offsets);
@@ -596,6 +607,10 @@ int xt_check_entry_offsets(const void *base, 
	if (target_offset + t->u.target_size > next_offset)

		return -EINVAL;



	if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&

	    target_offset + sizeof(struct xt_standard_target) != next_offset)

		return -EINVAL;



	return 0;

}

EXPORT_SYMBOL(xt_check_entry_offsets);