[PATCH] net: sctp: fix array overrun read on sctp_timer_tbl

[PATCH] net: sctp: fix array overrun read on sctp_timer_tbl

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

The comparison on the timeout can lead to an array overrun
read on sctp_timer_tbl because of an off-by-one error. Fix
this by using < instead of <= and also compare to the array
size rather than SCTP_EVENT_TIMEOUT_MAX.

Fixes CoverityScan CID#1397639 ("Out-of-bounds read")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 net/sctp/debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/debug.c b/net/sctp/debug.c
index 95d7b15..e371a0d 100644
--- a/net/sctp/debug.c
+++ b/net/sctp/debug.c
@@ -166,7 +166,7 @@ static const char *const sctp_timer_tbl[] = {
 /* Lookup timer debug name. */
 const char *sctp_tname(const sctp_subtype_t id)
 {
-	if (id.timeout <= SCTP_EVENT_TIMEOUT_MAX)
+	if (id.timeout < ARRAY_SIZE(sctp_timer_tbl))
 		return sctp_timer_tbl[id.timeout];
 	return "unknown_timer";
 }
-- 
2.10.2

Re: [PATCH] net: sctp: fix array overrun read on sctp_timer_tbl

[Marcelo Ricardo Leitner]

On Fri, Jan 20, 2017 at 01:01:57PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The comparison on the timeout can lead to an array overrun
> read on sctp_timer_tbl because of an off-by-one error. Fix
> this by using < instead of <= and also compare to the array
> size rather than SCTP_EVENT_TIMEOUT_MAX.
> 
> Fixes CoverityScan CID#1397639 ("Out-of-bounds read")
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  net/sctp/debug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sctp/debug.c b/net/sctp/debug.c
> index 95d7b15..e371a0d 100644
> --- a/net/sctp/debug.c
> +++ b/net/sctp/debug.c
> @@ -166,7 +166,7 @@ static const char *const sctp_timer_tbl[] = {
>  /* Lookup timer debug name. */
>  const char *sctp_tname(const sctp_subtype_t id)
>  {
> -	if (id.timeout <= SCTP_EVENT_TIMEOUT_MAX)
> +	if (id.timeout < ARRAY_SIZE(sctp_timer_tbl))
>  		return sctp_timer_tbl[id.timeout];

The issue exists but this is not the right fix.
Issue was introduced by 7b9438de0cd4 ("sctp: add stream reconf timer")
as it introduced a new timer but didn't add the timer name here, so the
fix should (also) include:

diff --git a/net/sctp/debug.c b/net/sctp/debug.c
index 95d7b15dad21..c5f4ed5242ac 100644
--- a/net/sctp/debug.c
+++ b/net/sctp/debug.c
@@ -159,6 +159,7 @@ static const char *const sctp_timer_tbl[] = {
 	"TIMEOUT_T4_RTO",
 	"TIMEOUT_T5_SHUTDOWN_GUARD",
 	"TIMEOUT_HEARTBEAT",
+	"TIMEOUT_RECONF",
 	"TIMEOUT_SACK",
 	"TIMEOUT_AUTOCLOSE",
 };

Thanks,
Marcelo

>  	return "unknown_timer";
>  }
> -- 
> 2.10.2
> 
> --
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> the body of a message to majordomo@vger.kernel.org
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> 

Re: [PATCH] net: sctp: fix array overrun read on sctp_timer_tbl

[Colin Ian King]

On 20/01/17 13:10, Marcelo Ricardo Leitner wrote:
> On Fri, Jan 20, 2017 at 01:01:57PM +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> The comparison on the timeout can lead to an array overrun
>> read on sctp_timer_tbl because of an off-by-one error. Fix
>> this by using < instead of <= and also compare to the array
>> size rather than SCTP_EVENT_TIMEOUT_MAX.
>>
>> Fixes CoverityScan CID#1397639 ("Out-of-bounds read")
>>
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  net/sctp/debug.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/sctp/debug.c b/net/sctp/debug.c
>> index 95d7b15..e371a0d 100644
>> --- a/net/sctp/debug.c
>> +++ b/net/sctp/debug.c
>> @@ -166,7 +166,7 @@ static const char *const sctp_timer_tbl[] = {
>>  /* Lookup timer debug name. */
>>  const char *sctp_tname(const sctp_subtype_t id)
>>  {
>> -	if (id.timeout <= SCTP_EVENT_TIMEOUT_MAX)
>> +	if (id.timeout < ARRAY_SIZE(sctp_timer_tbl))
>>  		return sctp_timer_tbl[id.timeout];
> 
> The issue exists but this is not the right fix.
> Issue was introduced by 7b9438de0cd4 ("sctp: add stream reconf timer")
> as it introduced a new timer but didn't add the timer name here, so the
> fix should (also) include:
> 
> diff --git a/net/sctp/debug.c b/net/sctp/debug.c
> index 95d7b15dad21..c5f4ed5242ac 100644
> --- a/net/sctp/debug.c
> +++ b/net/sctp/debug.c
> @@ -159,6 +159,7 @@ static const char *const sctp_timer_tbl[] = {
>  	"TIMEOUT_T4_RTO",
>  	"TIMEOUT_T5_SHUTDOWN_GUARD",
>  	"TIMEOUT_HEARTBEAT",
> +	"TIMEOUT_RECONF",
>  	"TIMEOUT_SACK",
>  	"TIMEOUT_AUTOCLOSE",
>  };

Ah, OK, I can add that timeout into the the table, but perhaps it's
still prudent to check the index against the table size as well.

> 
> Thanks,
> Marcelo
> 
>>  	return "unknown_timer";
>>  }
>> -- 
>> 2.10.2
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>

Re: [PATCH] net: sctp: fix array overrun read on sctp_timer_tbl

[Marcelo Ricardo Leitner]

On Fri, Jan 20, 2017 at 01:15:18PM +0000, Colin Ian King wrote:
> On 20/01/17 13:10, Marcelo Ricardo Leitner wrote:
> > On Fri, Jan 20, 2017 at 01:01:57PM +0000, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> The comparison on the timeout can lead to an array overrun
> >> read on sctp_timer_tbl because of an off-by-one error. Fix
> >> this by using < instead of <= and also compare to the array
> >> size rather than SCTP_EVENT_TIMEOUT_MAX.
> >>
> >> Fixes CoverityScan CID#1397639 ("Out-of-bounds read")
> >>
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >> ---
> >>  net/sctp/debug.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/net/sctp/debug.c b/net/sctp/debug.c
> >> index 95d7b15..e371a0d 100644
> >> --- a/net/sctp/debug.c
> >> +++ b/net/sctp/debug.c
> >> @@ -166,7 +166,7 @@ static const char *const sctp_timer_tbl[] = {
> >>  /* Lookup timer debug name. */
> >>  const char *sctp_tname(const sctp_subtype_t id)
> >>  {
> >> -	if (id.timeout <= SCTP_EVENT_TIMEOUT_MAX)
> >> +	if (id.timeout < ARRAY_SIZE(sctp_timer_tbl))
> >>  		return sctp_timer_tbl[id.timeout];
> > 
> > The issue exists but this is not the right fix.
> > Issue was introduced by 7b9438de0cd4 ("sctp: add stream reconf timer")
> > as it introduced a new timer but didn't add the timer name here, so the
> > fix should (also) include:
> > 
> > diff --git a/net/sctp/debug.c b/net/sctp/debug.c
> > index 95d7b15dad21..c5f4ed5242ac 100644
> > --- a/net/sctp/debug.c
> > +++ b/net/sctp/debug.c
> > @@ -159,6 +159,7 @@ static const char *const sctp_timer_tbl[] = {
> >  	"TIMEOUT_T4_RTO",
> >  	"TIMEOUT_T5_SHUTDOWN_GUARD",
> >  	"TIMEOUT_HEARTBEAT",
> > +	"TIMEOUT_RECONF",
> >  	"TIMEOUT_SACK",
> >  	"TIMEOUT_AUTOCLOSE",
> >  };
> 
> Ah, OK, I can add that timeout into the the table, but perhaps it's
> still prudent to check the index against the table size as well.
> 

Yes, and/or a:
  BUILD_BUG_ON(SCTP_EVENT_TIMEOUT_MAX + 1 != ARRAY_SIZE(sctp_timer_tbl))
As then we would be sure to have the list right :-)
Otherwise we may not do wrong reads but may report the wrong timer name.

> > 
> > Thanks,
> > Marcelo
> > 
> >>  	return "unknown_timer";
> >>  }
> >> -- 
> >> 2.10.2
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [PATCH] net: sctp: fix array overrun read on sctp_timer_tbl

[David Miller]

From: Colin King <colin.king@canonical.com>
Date: Fri, 20 Jan 2017 13:01:57 +0000

> From: Colin Ian King <colin.king@canonical.com>
> 
> The comparison on the timeout can lead to an array overrun
> read on sctp_timer_tbl because of an off-by-one error. Fix
> this by using < instead of <= and also compare to the array
> size rather than SCTP_EVENT_TIMEOUT_MAX.
> 
> Fixes CoverityScan CID#1397639 ("Out-of-bounds read")
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Applied.