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netfilter: x_tables: check standard target size too

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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>
This commit is contained in:
Florian Westphal 2016-04-01 14:17:27 +02:00 committed by Pablo Neira Ayuso
parent fc1221b3a1
commit 7ed2abddd2
1 changed files with 15 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

15
net/netfilter/x_tables.c
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@ -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);