[PATCH net] 6lowpan: Off by one handling ->nexthdr

[PATCH net] 6lowpan: Off by one handling ->nexthdr

[Dan Carpenter]

NEXTHDR_MAX is 255.  What happens here is that we take a u8 value
"hdr->nexthdr" from the network and then look it up in
lowpan_nexthdr_nhcs[].  The problem is that if hdr->nexthdr is 0xff then
we read one element beyond the end of the array so the array needs to
be one element larger.

Fixes: 92aa7c65d295 ("6lowpan: add generic nhc layer interface")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
This is the only place which uses the NEXTHDR_MAX define, so I considered
changing that to 256 instead.  Either fix would work.

 net/6lowpan/nhc.c  | 2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
index 4fa2fdda174d..9e56fb98f33c 100644
--- a/net/6lowpan/nhc.c
+++ b/net/6lowpan/nhc.c
@@ -18,7 +18,7 @@
 #include "nhc.h"
 
 static struct rb_root rb_root = RB_ROOT;
-static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
+static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
 static DEFINE_SPINLOCK(lowpan_nhc_lock);
 
 static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
-- 
2.17.1

Re: [PATCH net] 6lowpan: Off by one handling ->nexthdr

[Jukka Rissanen]

Hi Dan,

On Wed, 2019-04-03 at 08:34 +0300, Dan Carpenter wrote:
> NEXTHDR_MAX is 255.  What happens here is that we take a u8 value
> "hdr->nexthdr" from the network and then look it up in
> lowpan_nexthdr_nhcs[].  The problem is that if hdr->nexthdr is 0xff
> then
> we read one element beyond the end of the array so the array needs to
> be one element larger.
> 
> Fixes: 92aa7c65d295 ("6lowpan: add generic nhc layer interface")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This is the only place which uses the NEXTHDR_MAX define, so I
> considered
> changing that to 256 instead.  Either fix would work.
> 
>  net/6lowpan/nhc.c  | 2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
> index 4fa2fdda174d..9e56fb98f33c 100644
> --- a/net/6lowpan/nhc.c
> +++ b/net/6lowpan/nhc.c
> @@ -18,7 +18,7 @@
>  #include "nhc.h"
>  
>  static struct rb_root rb_root = RB_ROOT;
> -static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
> +static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
>  static DEFINE_SPINLOCK(lowpan_nhc_lock);
>  
>  static int lowpan_nhc_insert(struct lowpan_nhc *nhc)

Nice catch!

Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>


Cheers,
Jukka

Re: [PATCH net] 6lowpan: Off by one handling ->nexthdr

[Alexander Aring]

Hi,

On Wed, Apr 03, 2019 at 08:34:16AM +0300, Dan Carpenter wrote:
> NEXTHDR_MAX is 255.  What happens here is that we take a u8 value
> "hdr->nexthdr" from the network and then look it up in
> lowpan_nexthdr_nhcs[].  The problem is that if hdr->nexthdr is 0xff then
> we read one element beyond the end of the array so the array needs to
> be one element larger.
> 
> Fixes: 92aa7c65d295 ("6lowpan: add generic nhc layer interface")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Acked-by: Alexander Aring <aring@mojatatu.com>

Thanks.

- Alex

Re: [PATCH net] 6lowpan: Off by one handling ->nexthdr

[Marcel Holtmann]

Hi Dan,

> NEXTHDR_MAX is 255.  What happens here is that we take a u8 value
> "hdr->nexthdr" from the network and then look it up in
> lowpan_nexthdr_nhcs[].  The problem is that if hdr->nexthdr is 0xff then
> we read one element beyond the end of the array so the array needs to
> be one element larger.
> 
> Fixes: 92aa7c65d295 ("6lowpan: add generic nhc layer interface")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This is the only place which uses the NEXTHDR_MAX define, so I considered
> changing that to 256 instead.  Either fix would work.
> 
> net/6lowpan/nhc.c  | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel