* Re: [PATCH v2] netfilter: ebtables: fix fortify warnings
2023-08-08 16:32 ` Gustavo A. R. Silva
@ 2023-08-08 22:53 ` Kees Cook
2023-08-09 7:00 ` GONG, Ruiqi
2023-08-09 7:31 ` GONG, Ruiqi
2023-08-08 23:00 ` Kees Cook
2023-08-09 3:25 ` GONG, Ruiqi
2 siblings, 2 replies; 7+ messages in thread
From: Kees Cook @ 2023-08-08 22:53 UTC (permalink / raw)
To: Gustavo A. R. Silva, GONG, Ruiqi
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
Roopa Prabhu, Nikolay Aleksandrov, Kees Cook, netfilter-devel,
coreteam, netdev, linux-hardening, linux-kernel, Wang Weiyang,
Xiu Jianfeng, gongruiqi1
On August 8, 2023 9:32:50 AM PDT, "Gustavo A. R. Silva" <gustavoars@kernel.org> wrote:
>On Tue, Aug 08, 2023 at 09:30:38PM +0800, GONG, Ruiqi wrote:
>> From: "GONG, Ruiqi" <gongruiqi1@huawei.com>
>>
>> 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: GONG, Ruiqi <gongruiqi1@huawei.com>
>> ---
>>
>> v2: fix HDRTEST error by replacing struct_group() with __struct_group(),
>> since it's a uapi header.
>>
>> include/uapi/linux/netfilter_bridge/ebtables.h | 14 ++++++++------
>> net/bridge/netfilter/ebtables.c | 3 +--
>> 2 files changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/uapi/linux/netfilter_bridge/ebtables.h b/include/uapi/linux/netfilter_bridge/ebtables.h
>> index a494cf43a755..b0caad82b693 100644
>> --- a/include/uapi/linux/netfilter_bridge/ebtables.h
>> +++ b/include/uapi/linux/netfilter_bridge/ebtables.h
>> @@ -182,12 +182,14 @@ struct ebt_entry {
>> unsigned char sourcemsk[ETH_ALEN];
>> unsigned char destmac[ETH_ALEN];
>> unsigned char destmsk[ETH_ALEN];
>> - /* 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;
>> + __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))));
While we're here, can we drop this [0] in favor of []?
-Kees
>> };
>>
>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>> index 757ec46fc45a..5ec66b1ebb64 100644
>> --- a/net/bridge/netfilter/ebtables.c
>> +++ b/net/bridge/netfilter/ebtables.c
>> @@ -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(offsets) - sizeof(offsets[0]));
> ^^^^^^^^^^^^
>You now can replace this ____________________________________|
>with just `sizeof(entry->offsets)`
>
>With that change you can add my
>Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>
>Thank you
>--
>Gustavo
>
>>
>> if (state->buf_kern_start) {
>> buf_start = state->buf_kern_start + state->buf_kern_offset;
>> --
>> 2.41.0
>>
--
Kees Cook
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v2] netfilter: ebtables: fix fortify warnings
2023-08-08 22:53 ` Kees Cook
@ 2023-08-09 7:00 ` GONG, Ruiqi
2023-08-09 7:31 ` GONG, Ruiqi
1 sibling, 0 replies; 7+ messages in thread
From: GONG, Ruiqi @ 2023-08-09 7:00 UTC (permalink / raw)
To: Kees Cook, Gustavo A. R. Silva
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
Roopa Prabhu, Nikolay Aleksandrov, Kees Cook, netfilter-devel,
coreteam, netdev, linux-hardening, linux-kernel, Wang Weiyang,
Xiu Jianfeng, gongruiqi1
On 2023/08/09 6:53, Kees Cook wrote:
>
> [...]
>>>
>>> diff --git a/include/uapi/linux/netfilter_bridge/ebtables.h b/include/uapi/linux/netfilter_bridge/ebtables.h
>>> index a494cf43a755..b0caad82b693 100644
>>> --- a/include/uapi/linux/netfilter_bridge/ebtables.h
>>> +++ b/include/uapi/linux/netfilter_bridge/ebtables.h
>>> @@ -182,12 +182,14 @@ struct ebt_entry {
>>> unsigned char sourcemsk[ETH_ALEN];
>>> unsigned char destmac[ETH_ALEN];
>>> unsigned char destmsk[ETH_ALEN];
>>> - /* 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;
>>> + __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))));
>
> While we're here, can we drop this [0] in favor of []?
>
> -Kees
>
Look like it could be done. Will do in v3. Thanks!
>>> };
>>>
>>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>>> index 757ec46fc45a..5ec66b1ebb64 100644
>>> --- a/net/bridge/netfilter/ebtables.c
>>> +++ b/net/bridge/netfilter/ebtables.c
>>> @@ -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(offsets) - sizeof(offsets[0]));
>> ^^^^^^^^^^^^
>> You now can replace this ____________________________________|
>> with just `sizeof(entry->offsets)`
>>
>> With that change you can add my
>> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>
>> Thank you
>> --
>> Gustavo
>>
>>>
>>> if (state->buf_kern_start) {
>>> buf_start = state->buf_kern_start + state->buf_kern_offset;
>>> --
>>> 2.41.0
>>>
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v2] netfilter: ebtables: fix fortify warnings
2023-08-08 22:53 ` Kees Cook
2023-08-09 7:00 ` GONG, Ruiqi
@ 2023-08-09 7:31 ` GONG, Ruiqi
1 sibling, 0 replies; 7+ messages in thread
From: GONG, Ruiqi @ 2023-08-09 7:31 UTC (permalink / raw)
To: Kees Cook, Gustavo A. R. Silva, GONG, Ruiqi
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
Roopa Prabhu, Nikolay Aleksandrov, Kees Cook, netfilter-devel,
coreteam, netdev, linux-hardening, linux-kernel, Wang Weiyang,
Xiu Jianfeng
On 2023/08/09 6:53, Kees Cook wrote:
>
> [...]
>>>
>>> diff --git a/include/uapi/linux/netfilter_bridge/ebtables.h b/include/uapi/linux/netfilter_bridge/ebtables.h
>>> index a494cf43a755..b0caad82b693 100644
>>> --- a/include/uapi/linux/netfilter_bridge/ebtables.h
>>> +++ b/include/uapi/linux/netfilter_bridge/ebtables.h
>>> @@ -182,12 +182,14 @@ struct ebt_entry {
>>> unsigned char sourcemsk[ETH_ALEN];
>>> unsigned char destmac[ETH_ALEN];
>>> unsigned char destmsk[ETH_ALEN];
>>> - /* 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;
>>> + __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))));
>
> While we're here, can we drop this [0] in favor of []?
>
> -Kees
>
There are still quite a lot of zero-element array in
include/uapi/linux/netfilter_bridge/ebtables.h. I will submit another
patch to change them altogether.
>>> };
>>>
>>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>>> index 757ec46fc45a..5ec66b1ebb64 100644
>>> --- a/net/bridge/netfilter/ebtables.c
>>> +++ b/net/bridge/netfilter/ebtables.c
>>> @@ -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(offsets) - sizeof(offsets[0]));
>> ^^^^^^^^^^^^
>> You now can replace this ____________________________________|
>> with just `sizeof(entry->offsets)`
>>
>> With that change you can add my
>> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>
>> Thank you
>> --
>> Gustavo
>>
>>>
>>> if (state->buf_kern_start) {
>>> buf_start = state->buf_kern_start + state->buf_kern_offset;
>>> --
>>> 2.41.0
>>>
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] netfilter: ebtables: fix fortify warnings
2023-08-08 16:32 ` Gustavo A. R. Silva
2023-08-08 22:53 ` Kees Cook
@ 2023-08-08 23:00 ` Kees Cook
2023-08-09 3:25 ` GONG, Ruiqi
2 siblings, 0 replies; 7+ messages in thread
From: Kees Cook @ 2023-08-08 23:00 UTC (permalink / raw)
To: Gustavo A. R. Silva, GONG, Ruiqi
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
Roopa Prabhu, Nikolay Aleksandrov, Kees Cook, netfilter-devel,
coreteam, netdev, linux-hardening, linux-kernel, Wang Weiyang,
Xiu Jianfeng, gongruiqi1
On August 8, 2023 9:32:50 AM PDT, "Gustavo A. R. Silva" <gustavoars@kernel.org> wrote:
>On Tue, Aug 08, 2023 at 09:30:38PM +0800, GONG, Ruiqi wrote:
>> From: "GONG, Ruiqi" <gongruiqi1@huawei.com>
>>
>> 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: GONG, Ruiqi <gongruiqi1@huawei.com>
>> ---
>>
>> v2: fix HDRTEST error by replacing struct_group() with __struct_group(),
>> since it's a uapi header.
>>
>> include/uapi/linux/netfilter_bridge/ebtables.h | 14 ++++++++------
>> net/bridge/netfilter/ebtables.c | 3 +--
>> 2 files changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/uapi/linux/netfilter_bridge/ebtables.h b/include/uapi/linux/netfilter_bridge/ebtables.h
>> index a494cf43a755..b0caad82b693 100644
>> --- a/include/uapi/linux/netfilter_bridge/ebtables.h
>> +++ b/include/uapi/linux/netfilter_bridge/ebtables.h
>> @@ -182,12 +182,14 @@ struct ebt_entry {
>> unsigned char sourcemsk[ETH_ALEN];
>> unsigned char destmac[ETH_ALEN];
>> unsigned char destmsk[ETH_ALEN];
>> - /* 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;
>> + __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))));
>> };
Actually, looking at what size_entry_mwt() is doing, I think you probably DO want a tag for this and to use a real structure for the manipulations instead of doing array indexing? I dunno. This is a weird function! :)
-Kees
>>
>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>> index 757ec46fc45a..5ec66b1ebb64 100644
>> --- a/net/bridge/netfilter/ebtables.c
>> +++ b/net/bridge/netfilter/ebtables.c
>> @@ -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(offsets) - sizeof(offsets[0]));
> ^^^^^^^^^^^^
>You now can replace this ____________________________________|
>with just `sizeof(entry->offsets)`
>
>With that change you can add my
>Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>
>Thank you
>--
>Gustavo
>
>>
>> if (state->buf_kern_start) {
>> buf_start = state->buf_kern_start + state->buf_kern_offset;
>> --
>> 2.41.0
>>
--
Kees Cook
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v2] netfilter: ebtables: fix fortify warnings
2023-08-08 16:32 ` Gustavo A. R. Silva
2023-08-08 22:53 ` Kees Cook
2023-08-08 23:00 ` Kees Cook
@ 2023-08-09 3:25 ` GONG, Ruiqi
2 siblings, 0 replies; 7+ messages in thread
From: GONG, Ruiqi @ 2023-08-09 3:25 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
Roopa Prabhu, Nikolay Aleksandrov, Kees Cook, netfilter-devel,
coreteam, netdev, linux-hardening, linux-kernel, Wang Weiyang,
Xiu Jianfeng, gongruiqi1
On 2023/08/09 0:32, Gustavo A. R. Silva wrote:
>
> [...]
>
>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>> index 757ec46fc45a..5ec66b1ebb64 100644
>> --- a/net/bridge/netfilter/ebtables.c
>> +++ b/net/bridge/netfilter/ebtables.c
>> @@ -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(offsets) - sizeof(offsets[0]));
> ^^^^^^^^^^^^
> You now can replace this ____________________________________|
> with just `sizeof(entry->offsets)`
>
> With that change you can add my
> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>
> Thank you
> --
> Gustavo
>
Will do. Thanks for the suggestion & review!
>>
>> if (state->buf_kern_start) {
>> buf_start = state->buf_kern_start + state->buf_kern_offset;
>> --
>> 2.41.0
>>
^ permalink raw reply [flat|nested] 7+ messages in thread