[PATCH] powerpc/pseries: avoid blocking in irq when queuing hotplug events

[PATCH] powerpc/pseries: avoid blocking in irq when queuing hotplug events

[Nathan Lynch]

A couple of bugs in queue_hotplug_event():

1. Unchecked kmalloc result which could lead to an oops.
2. Use of GFP_KERNEL allocations in interrupt context (this code's
   only caller is ras_hotplug_interrupt()).

Use kmemdup to avoid open-coding the allocation+copy and check for
failure; use GFP_ATOMIC for both allocations.

Ultimately it probably would be better to avoid or reduce allocations
in this path if possible.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
---

Found by inspection, built but not runtime-tested.

 arch/powerpc/platforms/pseries/dlpar.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
index 17958043e7f7..d70f9b925378 100644
--- a/arch/powerpc/platforms/pseries/dlpar.c
+++ b/arch/powerpc/platforms/pseries/dlpar.c
@@ -386,11 +386,11 @@ void queue_hotplug_event(struct pseries_hp_errorlog *hp_errlog)
 	struct pseries_hp_work *work;
 	struct pseries_hp_errorlog *hp_errlog_copy;
 
-	hp_errlog_copy = kmalloc(sizeof(struct pseries_hp_errorlog),
-				 GFP_KERNEL);
-	memcpy(hp_errlog_copy, hp_errlog, sizeof(struct pseries_hp_errorlog));
+	hp_errlog_copy = kmemdup(hp_errlog, sizeof(*hp_errlog), GFP_ATOMIC);
+	if (!hp_errlog_copy)
+		return;
 
-	work = kmalloc(sizeof(struct pseries_hp_work), GFP_KERNEL);
+	work = kmalloc(sizeof(struct pseries_hp_work), GFP_ATOMIC);
 	if (work) {
 		INIT_WORK((struct work_struct *)work, pseries_hp_work_fn);
 		work->errlog = hp_errlog_copy;
-- 
2.20.1

Re: [PATCH] powerpc/pseries: avoid blocking in irq when queuing hotplug events

[Michael Ellerman]

On Tue, 2019-05-28 at 23:28:01 UTC, Nathan Lynch wrote:
> A couple of bugs in queue_hotplug_event():
> 
> 1. Unchecked kmalloc result which could lead to an oops.
> 2. Use of GFP_KERNEL allocations in interrupt context (this code's
>    only caller is ras_hotplug_interrupt()).
> 
> Use kmemdup to avoid open-coding the allocation+copy and check for
> failure; use GFP_ATOMIC for both allocations.
> 
> Ultimately it probably would be better to avoid or reduce allocations
> in this path if possible.
> 
> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/348ea30f51fc63ce3c7fd7dba6043e8e3ee0ef34

cheers