[PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[Laura Abbott]

The sizes for memcpy in flow_offload_mangle don't match
the source variables, leading to overflow errors on some
build configurations:

In function 'memcpy',
    inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
    inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
    inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
  376 |    __read_overflow2();
      |    ^~~~~~~~~~~~~~~~~~
make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1

Fix this by using the corresponding type.

Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Laura Abbott <labbott@redhat.com>
---
Seen on a Fedora powerpc little endian build with -O3 but it looks like
it is correctly catching an error with doing a memcpy outside the source
variable.
---
 net/netfilter/nf_flow_table_offload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index c54c9a6cc981..526f894d0bdb 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
 	entry->id = FLOW_ACTION_MANGLE;
 	entry->mangle.htype = htype;
 	entry->mangle.offset = offset;
-	memcpy(&entry->mangle.mask, mask, sizeof(u32));
-	memcpy(&entry->mangle.val, value, sizeof(u32));
+	memcpy(&entry->mangle.mask, mask, sizeof(u8));
+	memcpy(&entry->mangle.val, value, sizeof(u8));
 }
 
 static inline struct flow_action_entry *
-- 
2.21.0

Re: [PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[Marcelo Ricardo Leitner]

On Tue, Dec 03, 2019 at 11:03:45AM -0500, Laura Abbott wrote:
> The sizes for memcpy in flow_offload_mangle don't match
> the source variables, leading to overflow errors on some
> build configurations:
> 
> In function 'memcpy',
>     inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
>     inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
>     inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
> ./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
>   376 |    __read_overflow2();
>       |    ^~~~~~~~~~~~~~~~~~
> make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1
> 
> Fix this by using the corresponding type.
> 
> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
> Seen on a Fedora powerpc little endian build with -O3 but it looks like
> it is correctly catching an error with doing a memcpy outside the source
> variable.

Hi,

It is right but the fix is not. In that call trace:

flow_offload_port_dnat() {
...
        u32 mask = ~htonl(0xffff);
        __be16 port;
...
        flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
	                            (u8 *)&port, (u8 *)&mask);
}

port should have a 32b storage as well, and aligned with the mask.

> ---
>  net/netfilter/nf_flow_table_offload.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> index c54c9a6cc981..526f894d0bdb 100644
> --- a/net/netfilter/nf_flow_table_offload.c
> +++ b/net/netfilter/nf_flow_table_offload.c
> @@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
>  	entry->id = FLOW_ACTION_MANGLE;
>  	entry->mangle.htype = htype;
>  	entry->mangle.offset = offset;
> -	memcpy(&entry->mangle.mask, mask, sizeof(u32));
> -	memcpy(&entry->mangle.val, value, sizeof(u32));
                                   ^^^^^         ^^^ which is &port in the call above
> +	memcpy(&entry->mangle.mask, mask, sizeof(u8));
> +	memcpy(&entry->mangle.val, value, sizeof(u8));

This fix would cause it to copy only the first byte, which is not the
intention.

>  }
>  
>  static inline struct flow_action_entry *
> -- 
> 2.21.0
> 

Re: [PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[Laura Abbott]

On 12/3/19 12:01 PM, Marcelo Ricardo Leitner wrote:
> On Tue, Dec 03, 2019 at 11:03:45AM -0500, Laura Abbott wrote:
>> The sizes for memcpy in flow_offload_mangle don't match
>> the source variables, leading to overflow errors on some
>> build configurations:
>>
>> In function 'memcpy',
>>      inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
>>      inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
>>      inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
>> ./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
>>    376 |    __read_overflow2();
>>        |    ^~~~~~~~~~~~~~~~~~
>> make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1
>>
>> Fix this by using the corresponding type.
>>
>> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
>> Signed-off-by: Laura Abbott <labbott@redhat.com>
>> ---
>> Seen on a Fedora powerpc little endian build with -O3 but it looks like
>> it is correctly catching an error with doing a memcpy outside the source
>> variable.
> 
> Hi,
> 
> It is right but the fix is not. In that call trace:
> 
> flow_offload_port_dnat() {
> ...
>          u32 mask = ~htonl(0xffff);
>          __be16 port;
> ...
>          flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
> 	                            (u8 *)&port, (u8 *)&mask);
> }
> 
> port should have a 32b storage as well, and aligned with the mask.
> 
>> ---
>>   net/netfilter/nf_flow_table_offload.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
>> index c54c9a6cc981..526f894d0bdb 100644
>> --- a/net/netfilter/nf_flow_table_offload.c
>> +++ b/net/netfilter/nf_flow_table_offload.c
>> @@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
>>   	entry->id = FLOW_ACTION_MANGLE;
>>   	entry->mangle.htype = htype;
>>   	entry->mangle.offset = offset;
>> -	memcpy(&entry->mangle.mask, mask, sizeof(u32));
>> -	memcpy(&entry->mangle.val, value, sizeof(u32));
>                                     ^^^^^         ^^^ which is &port in the call above
>> +	memcpy(&entry->mangle.mask, mask, sizeof(u8));
>> +	memcpy(&entry->mangle.val, value, sizeof(u8));
> 
> This fix would cause it to copy only the first byte, which is not the
> intention.
>

Thanks for the review. I took another look at fixing this and I
think it might be better for the maintainer or someone who is more
familiar with the code to fix this. I ended up down a rabbit
hole trying to get the types to work and I wasn't confident about
the casting.

Thanks,
Laura
  
>>   }
>>   
>>   static inline struct flow_action_entry *
>> -- 
>> 2.21.0
>>
> 

Re: [PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[Justin Forbes]

On Tue, Dec 3, 2019 at 2:50 PM Laura Abbott <labbott@redhat.com> wrote:
>
> On 12/3/19 12:01 PM, Marcelo Ricardo Leitner wrote:
> > On Tue, Dec 03, 2019 at 11:03:45AM -0500, Laura Abbott wrote:
> >> The sizes for memcpy in flow_offload_mangle don't match
> >> the source variables, leading to overflow errors on some
> >> build configurations:
> >>
> >> In function 'memcpy',
> >>      inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
> >>      inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
> >>      inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
> >> ./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
> >>    376 |    __read_overflow2();
> >>        |    ^~~~~~~~~~~~~~~~~~
> >> make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1
> >>
> >> Fix this by using the corresponding type.
> >>
> >> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
> >> Signed-off-by: Laura Abbott <labbott@redhat.com>
> >> ---
> >> Seen on a Fedora powerpc little endian build with -O3 but it looks like
> >> it is correctly catching an error with doing a memcpy outside the source
> >> variable.
> >
> > Hi,
> >
> > It is right but the fix is not. In that call trace:
> >
> > flow_offload_port_dnat() {
> > ...
> >          u32 mask = ~htonl(0xffff);
> >          __be16 port;
> > ...
> >          flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
> >                                   (u8 *)&port, (u8 *)&mask);
> > }
> >
> > port should have a 32b storage as well, and aligned with the mask.
> >
> >> ---
> >>   net/netfilter/nf_flow_table_offload.c | 4 ++--
> >>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> >> index c54c9a6cc981..526f894d0bdb 100644
> >> --- a/net/netfilter/nf_flow_table_offload.c
> >> +++ b/net/netfilter/nf_flow_table_offload.c
> >> @@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
> >>      entry->id = FLOW_ACTION_MANGLE;
> >>      entry->mangle.htype = htype;
> >>      entry->mangle.offset = offset;
> >> -    memcpy(&entry->mangle.mask, mask, sizeof(u32));
> >> -    memcpy(&entry->mangle.val, value, sizeof(u32));
> >                                     ^^^^^         ^^^ which is &port in the call above
> >> +    memcpy(&entry->mangle.mask, mask, sizeof(u8));
> >> +    memcpy(&entry->mangle.val, value, sizeof(u8));
> >
> > This fix would cause it to copy only the first byte, which is not the
> > intention.
> >
>
> Thanks for the review. I took another look at fixing this and I
> think it might be better for the maintainer or someone who is more
> familiar with the code to fix this. I ended up down a rabbit
> hole trying to get the types to work and I wasn't confident about
> the casting.
>

Any update on this? It is definitely a problem on PPC LE.

Thanks,
Justin

Re: [PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[Pablo Neira Ayuso]

[-- Attachment #1: Type: text/plain, Size: 3380 bytes --]

On Fri, Dec 06, 2019 at 04:58:30PM -0600, Justin Forbes wrote:
> On Tue, Dec 3, 2019 at 2:50 PM Laura Abbott <labbott@redhat.com> wrote:
> >
> > On 12/3/19 12:01 PM, Marcelo Ricardo Leitner wrote:
> > > On Tue, Dec 03, 2019 at 11:03:45AM -0500, Laura Abbott wrote:
> > >> The sizes for memcpy in flow_offload_mangle don't match
> > >> the source variables, leading to overflow errors on some
> > >> build configurations:
> > >>
> > >> In function 'memcpy',
> > >>      inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
> > >>      inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
> > >>      inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
> > >> ./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
> > >>    376 |    __read_overflow2();
> > >>        |    ^~~~~~~~~~~~~~~~~~
> > >> make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1
> > >>
> > >> Fix this by using the corresponding type.
> > >>
> > >> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
> > >> Signed-off-by: Laura Abbott <labbott@redhat.com>
> > >> ---
> > >> Seen on a Fedora powerpc little endian build with -O3 but it looks like
> > >> it is correctly catching an error with doing a memcpy outside the source
> > >> variable.
> > >
> > > Hi,
> > >
> > > It is right but the fix is not. In that call trace:
> > >
> > > flow_offload_port_dnat() {
> > > ...
> > >          u32 mask = ~htonl(0xffff);
> > >          __be16 port;
> > > ...
> > >          flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
> > >                                   (u8 *)&port, (u8 *)&mask);
> > > }
> > >
> > > port should have a 32b storage as well, and aligned with the mask.
> > >
> > >> ---
> > >>   net/netfilter/nf_flow_table_offload.c | 4 ++--
> > >>   1 file changed, 2 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> > >> index c54c9a6cc981..526f894d0bdb 100644
> > >> --- a/net/netfilter/nf_flow_table_offload.c
> > >> +++ b/net/netfilter/nf_flow_table_offload.c
> > >> @@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
> > >>      entry->id = FLOW_ACTION_MANGLE;
> > >>      entry->mangle.htype = htype;
> > >>      entry->mangle.offset = offset;
> > >> -    memcpy(&entry->mangle.mask, mask, sizeof(u32));
> > >> -    memcpy(&entry->mangle.val, value, sizeof(u32));
> > >                                     ^^^^^         ^^^ which is &port in the call above
> > >> +    memcpy(&entry->mangle.mask, mask, sizeof(u8));
> > >> +    memcpy(&entry->mangle.val, value, sizeof(u8));
> > >
> > > This fix would cause it to copy only the first byte, which is not the
> > > intention.
> > >
> >
> > Thanks for the review. I took another look at fixing this and I
> > think it might be better for the maintainer or someone who is more
> > familiar with the code to fix this. I ended up down a rabbit
> > hole trying to get the types to work and I wasn't confident about
> > the casting.
> 
> Any update on this? It is definitely a problem on PPC LE.

I'm attaching a tentative patch to address this problem.

Thanks.

[-- Attachment #2: x.patch --]
[-- Type: text/x-diff, Size: 2089 bytes --]

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index 30205d57226d..cfa5602f54f5 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -336,23 +336,22 @@ static void flow_offload_port_snat(struct net *net,
 				   struct nf_flow_rule *flow_rule)
 {
 	struct flow_action_entry *entry = flow_action_entry_next(flow_rule);
-	u32 mask = ~htonl(0xffff0000);
-	__be16 port;
+	u32 mask = ~htonl(0xffff0000), port;
 	u32 offset;
 
 	switch (dir) {
 	case FLOW_OFFLOAD_DIR_ORIGINAL:
-		port = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_port;
+		port = ntohs(flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_port);
 		offset = 0; /* offsetof(struct tcphdr, source); */
 		break;
 	case FLOW_OFFLOAD_DIR_REPLY:
-		port = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_port;
+		port = ntohs(flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_port);
 		offset = 0; /* offsetof(struct tcphdr, dest); */
 		break;
 	default:
 		return;
 	}
-
+	port = htonl(port << 16);
 	flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
 			    (u8 *)&port, (u8 *)&mask);
 }
@@ -363,23 +362,22 @@ static void flow_offload_port_dnat(struct net *net,
 				   struct nf_flow_rule *flow_rule)
 {
 	struct flow_action_entry *entry = flow_action_entry_next(flow_rule);
-	u32 mask = ~htonl(0xffff);
-	__be16 port;
+	u32 mask = ~htonl(0xffff), port;
 	u32 offset;
 
 	switch (dir) {
 	case FLOW_OFFLOAD_DIR_ORIGINAL:
-		port = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_port;
+		port = ntohs(flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_port);
 		offset = 0; /* offsetof(struct tcphdr, source); */
 		break;
 	case FLOW_OFFLOAD_DIR_REPLY:
-		port = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_port;
+		port = ntohs(flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_port);
 		offset = 0; /* offsetof(struct tcphdr, dest); */
 		break;
 	default:
 		return;
 	}
-
+	port = htonl(port);
 	flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
 			    (u8 *)&port, (u8 *)&mask);
 }

Re: [PATCH] netfilter: nf_flow_table_offload: Correct memcpy size for flow_overload_mangle

[Justin Forbes]

On Sat, Dec 7, 2019 at 11:38 AM Pablo Neira Ayuso <pablo@netfilter.org> wrote:
>
> On Fri, Dec 06, 2019 at 04:58:30PM -0600, Justin Forbes wrote:
> > On Tue, Dec 3, 2019 at 2:50 PM Laura Abbott <labbott@redhat.com> wrote:
> > >
> > > On 12/3/19 12:01 PM, Marcelo Ricardo Leitner wrote:
> > > > On Tue, Dec 03, 2019 at 11:03:45AM -0500, Laura Abbott wrote:
> > > >> The sizes for memcpy in flow_offload_mangle don't match
> > > >> the source variables, leading to overflow errors on some
> > > >> build configurations:
> > > >>
> > > >> In function 'memcpy',
> > > >>      inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
> > > >>      inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
> > > >>      inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
> > > >> ./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
> > > >>    376 |    __read_overflow2();
> > > >>        |    ^~~~~~~~~~~~~~~~~~
> > > >> make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1
> > > >>
> > > >> Fix this by using the corresponding type.
> > > >>
> > > >> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
> > > >> Signed-off-by: Laura Abbott <labbott@redhat.com>
> > > >> ---
> > > >> Seen on a Fedora powerpc little endian build with -O3 but it looks like
> > > >> it is correctly catching an error with doing a memcpy outside the source
> > > >> variable.
> > > >
> > > > Hi,
> > > >
> > > > It is right but the fix is not. In that call trace:
> > > >
> > > > flow_offload_port_dnat() {
> > > > ...
> > > >          u32 mask = ~htonl(0xffff);
> > > >          __be16 port;
> > > > ...
> > > >          flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
> > > >                                   (u8 *)&port, (u8 *)&mask);
> > > > }
> > > >
> > > > port should have a 32b storage as well, and aligned with the mask.
> > > >
> > > >> ---
> > > >>   net/netfilter/nf_flow_table_offload.c | 4 ++--
> > > >>   1 file changed, 2 insertions(+), 2 deletions(-)
> > > >>
> > > >> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> > > >> index c54c9a6cc981..526f894d0bdb 100644
> > > >> --- a/net/netfilter/nf_flow_table_offload.c
> > > >> +++ b/net/netfilter/nf_flow_table_offload.c
> > > >> @@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
> > > >>      entry->id = FLOW_ACTION_MANGLE;
> > > >>      entry->mangle.htype = htype;
> > > >>      entry->mangle.offset = offset;
> > > >> -    memcpy(&entry->mangle.mask, mask, sizeof(u32));
> > > >> -    memcpy(&entry->mangle.val, value, sizeof(u32));
> > > >                                     ^^^^^         ^^^ which is &port in the call above
> > > >> +    memcpy(&entry->mangle.mask, mask, sizeof(u8));
> > > >> +    memcpy(&entry->mangle.val, value, sizeof(u8));
> > > >
> > > > This fix would cause it to copy only the first byte, which is not the
> > > > intention.
> > > >
> > >
> > > Thanks for the review. I took another look at fixing this and I
> > > think it might be better for the maintainer or someone who is more
> > > familiar with the code to fix this. I ended up down a rabbit
> > > hole trying to get the types to work and I wasn't confident about
> > > the casting.
> >
> > Any update on this? It is definitely a problem on PPC LE.
>
> I'm attaching a tentative patch to address this problem.
>
This patch does in fact fix the build issue.

Thanks,
Justin