Commit a7ed3465 authored by GONG, Ruiqi's avatar GONG, Ruiqi Committed by Florian Westphal
Browse files

netfilter: ebtables: fix fortify warnings in size_entry_mwt() 



When compiling with gcc 13 and CONFIG_FORTIFY_SOURCE=y, the following
warning appears:

In function ‘fortify_memcpy_chk’,
    inlined from ‘size_entry_mwt’ at net/bridge/netfilter/ebtables.c:2118:2:
./include/linux/fortify-string.h:592:25: error: call to ‘__read_overflow2_field’
declared with attribute warning: detected read beyond size of field (2nd parameter);
maybe use struct_group()? [-Werror=attribute-warning]
  592 |                         __read_overflow2_field(q_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The compiler is complaining:

memcpy(&offsets[1], &entry->watchers_offset,
                       sizeof(offsets) - sizeof(offsets[0]));

where memcpy reads beyong &entry->watchers_offset to copy
{watchers,target,next}_offset altogether into offsets[]. Silence the
warning by wrapping these three up via struct_group().

Signed-off-by: default avatarGONG, Ruiqi <gongruiqi1@huawei.com>
Reviewed-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
parent 43c28172

include/uapi/linux/netfilter_bridge/ebtables.h

+8 −6
Original line number Diff line number Diff line
@@ -182,12 +182,14 @@ struct ebt_entry { 
	unsigned char sourcemsk[ETH_ALEN];

	unsigned char destmac[ETH_ALEN];

	unsigned char destmsk[ETH_ALEN];

	__struct_group(/* no tag */, offsets, /* no attrs */,

		/* sizeof ebt_entry + matches */

		unsigned int watchers_offset;

		/* sizeof ebt_entry + matches + watchers */

		unsigned int target_offset;

		/* sizeof ebt_entry + matches + watchers + target */

		unsigned int next_offset;

	);

	unsigned char elems[0] __attribute__ ((aligned (__alignof__(struct ebt_replace))));

};

net/bridge/netfilter/ebtables.c

+1 −2
Original line number Diff line number Diff line
@@ -2115,8 +2115,7 @@ static int size_entry_mwt(const struct ebt_entry *entry, const unsigned char *ba 
		return ret;



	offsets[0] = sizeof(struct ebt_entry); /* matches come first */

	memcpy(&offsets[1], &entry->watchers_offset,

			sizeof(offsets) - sizeof(offsets[0]));

	memcpy(&offsets[1], &entry->offsets, sizeof(entry->offsets));



	if (state->buf_kern_start) {

		buf_start = state->buf_kern_start + state->buf_kern_offset;