[PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Dan Carpenter]

The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
>= to prevent a read one element beyond the end of the array.

Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 78b602cae6c2..f49966713ac3 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
 		*bug_id = atomic_inc_return(&csd_bug_count);
 	cpu = csd_lock_wait_getcpu(csd);
 	smp_mb(); // No stale cur_csd values!
-	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
+	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
 		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
 	else
 		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
-- 
2.27.0

[PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Dan Carpenter]

The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
>= to prevent a read one element beyond the end of the array.

Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 78b602cae6c2..f49966713ac3 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
 		*bug_id = atomic_inc_return(&csd_bug_count);
 	cpu = csd_lock_wait_getcpu(csd);
 	smp_mb(); // No stale cur_csd values!
-	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
+	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
 		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
 	else
 		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
-- 
2.27.0

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Peter Zijlstra]

On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> >= to prevent a read one element beyond the end of the array.
> 
> Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")

I don't have a copy of that patch in my inbox, even though it says Cc:
me.

Paul, where do you expect that patch to go? The version I see from my
next tree needs a _lot_ of work.

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  kernel/smp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 78b602cae6c2..f49966713ac3 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
>  		*bug_id = atomic_inc_return(&csd_bug_count);
>  	cpu = csd_lock_wait_getcpu(csd);
>  	smp_mb(); // No stale cur_csd values!
> -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
>  	else
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> -- 
> 2.27.0
> 

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Peter Zijlstra]

On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> >= to prevent a read one element beyond the end of the array.
> 
> Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")

I don't have a copy of that patch in my inbox, even though it says Cc:
me.

Paul, where do you expect that patch to go? The version I see from my
next tree needs a _lot_ of work.

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  kernel/smp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 78b602cae6c2..f49966713ac3 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
>  		*bug_id = atomic_inc_return(&csd_bug_count);
>  	cpu = csd_lock_wait_getcpu(csd);
>  	smp_mb(); // No stale cur_csd values!
> -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
>  	else
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> -- 
> 2.27.0
> 

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Sebastian Andrzej Siewior]

On 2020-07-09 12:59:06 [+0200], Peter Zijlstra wrote:
> On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> > >= to prevent a read one element beyond the end of the array.
> > 
> > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> 
> I don't have a copy of that patch in my inbox, even though it says Cc:
> me.
> 
> Paul, where do you expect that patch to go? The version I see from my
> next tree needs a _lot_ of work.

There is also
 
 https://lkml.kernel.org/r/20200705082603.GX3874@shao2-debian
 https://lkml.kernel.org/r/00000000000042f21905a991ecea@google.com

it might be the same thing.

Sebastian

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Sebastian Andrzej Siewior]

On 2020-07-09 12:59:06 [+0200], Peter Zijlstra wrote:
> On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> > >= to prevent a read one element beyond the end of the array.
> > 
> > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> 
> I don't have a copy of that patch in my inbox, even though it says Cc:
> me.
> 
> Paul, where do you expect that patch to go? The version I see from my
> next tree needs a _lot_ of work.

There is also
 
 https://lkml.kernel.org/r/20200705082603.GX3874@shao2-debian
 https://lkml.kernel.org/r/00000000000042f21905a991ecea@google.com

it might be the same thing.

Sebastian

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Paul E. McKenney]

On Thu, Jul 09, 2020 at 12:59:06PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> > >= to prevent a read one element beyond the end of the array.
> > 
> > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")

Good catch, will apply, thank you!

> I don't have a copy of that patch in my inbox, even though it says Cc:
> me.

I wasn't going to bother you with it until a bit after v5.9-rc1.
But it appears that this don't-bother-you strategy failed.

> Paul, where do you expect that patch to go? The version I see from my
> next tree needs a _lot_ of work.

I expect it to go nowhere until at least the v5.10 merge window.

							Thanx, Paul

> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> >  kernel/smp.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/smp.c b/kernel/smp.c
> > index 78b602cae6c2..f49966713ac3 100644
> > --- a/kernel/smp.c
> > +++ b/kernel/smp.c
> > @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
> >  		*bug_id = atomic_inc_return(&csd_bug_count);
> >  	cpu = csd_lock_wait_getcpu(csd);
> >  	smp_mb(); // No stale cur_csd values!
> > -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> > +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> >  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
> >  	else
> >  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> > -- 
> > 2.27.0
> > 

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Paul E. McKenney]

On Thu, Jul 09, 2020 at 12:59:06PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> > >= to prevent a read one element beyond the end of the array.
> > 
> > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")

Good catch, will apply, thank you!

> I don't have a copy of that patch in my inbox, even though it says Cc:
> me.

I wasn't going to bother you with it until a bit after v5.9-rc1.
But it appears that this don't-bother-you strategy failed.

> Paul, where do you expect that patch to go? The version I see from my
> next tree needs a _lot_ of work.

I expect it to go nowhere until at least the v5.10 merge window.

							Thanx, Paul

> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> >  kernel/smp.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/smp.c b/kernel/smp.c
> > index 78b602cae6c2..f49966713ac3 100644
> > --- a/kernel/smp.c
> > +++ b/kernel/smp.c
> > @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
> >  		*bug_id = atomic_inc_return(&csd_bug_count);
> >  	cpu = csd_lock_wait_getcpu(csd);
> >  	smp_mb(); // No stale cur_csd values!
> > -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> > +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> >  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
> >  	else
> >  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> > -- 
> > 2.27.0
> > 

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Paul E. McKenney]

On Thu, Jul 09, 2020 at 01:49:00PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-07-09 12:59:06 [+0200], Peter Zijlstra wrote:
> > On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> > > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> > > >= to prevent a read one element beyond the end of the array.
> > > 
> > > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> > 
> > I don't have a copy of that patch in my inbox, even though it says Cc:
> > me.
> > 
> > Paul, where do you expect that patch to go? The version I see from my
> > next tree needs a _lot_ of work.
> 
> There is also
>  
>  https://lkml.kernel.org/r/20200705082603.GX3874@shao2-debian
>  https://lkml.kernel.org/r/00000000000042f21905a991ecea@google.com
> 
> it might be the same thing.

Same commit, different bug, but the fix should be in -next by now.
For these two reports, the problem was that I had debug-recording code
on the wrong side of a csd_unlock().

							Thanx, Paul

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Paul E. McKenney]

On Thu, Jul 09, 2020 at 01:49:00PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-07-09 12:59:06 [+0200], Peter Zijlstra wrote:
> > On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> > > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> > > >= to prevent a read one element beyond the end of the array.
> > > 
> > > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> > 
> > I don't have a copy of that patch in my inbox, even though it says Cc:
> > me.
> > 
> > Paul, where do you expect that patch to go? The version I see from my
> > next tree needs a _lot_ of work.
> 
> There is also
>  
>  https://lkml.kernel.org/r/20200705082603.GX3874@shao2-debian
>  https://lkml.kernel.org/r/00000000000042f21905a991ecea@google.com
> 
> it might be the same thing.

Same commit, different bug, but the fix should be in -next by now.
For these two reports, the problem was that I had debug-recording code
on the wrong side of a csd_unlock().

							Thanx, Paul

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Paul E. McKenney]

On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> >= to prevent a read one element beyond the end of the array.
> 
> Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Good eyes, thank you!  Folding this into the original with
attribution.

							Thanx, Paul

> ---
>  kernel/smp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 78b602cae6c2..f49966713ac3 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
>  		*bug_id = atomic_inc_return(&csd_bug_count);
>  	cpu = csd_lock_wait_getcpu(csd);
>  	smp_mb(); // No stale cur_csd values!
> -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
>  	else
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> -- 
> 2.27.0
> 

Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()

[Paul E. McKenney]

On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> >= to prevent a read one element beyond the end of the array.
> 
> Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Good eyes, thank you!  Folding this into the original with
attribution.

							Thanx, Paul

> ---
>  kernel/smp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 78b602cae6c2..f49966713ac3 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
>  		*bug_id = atomic_inc_return(&csd_bug_count);
>  	cpu = csd_lock_wait_getcpu(csd);
>  	smp_mb(); // No stale cur_csd values!
> -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
>  	else
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> -- 
> 2.27.0
>