[PATCH] mm/tracing: Add check for kmem_cache

[Jiasheng Jiang]

In __kmem_cache_alloc_lru() of mm/slab.c, cachep may be NULL when error
occurs in slab_alloc().
However, trace_kmem_cache_alloc() will still use it as the parameter,
which may cause NULL poineter dereference.
Therefore, it should be better to add the check and handle the error
in the trace_kmem_cache_alloc().

Fixes: 36555751c675 ("kmemtrace: SLAB hooks.")
Signed-off-by: Jiasheng Jiang <jiasheng@xxxxxxxxxxx>
---
 include/trace/events/kmem.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 243073cfc29d..d99507d32ef5 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -32,8 +32,8 @@ TRACE_EVENT(kmem_cache_alloc,
 	TP_fast_assign(
 		__entry->call_site	= call_site;
 		__entry->ptr		= ptr;
-		__entry->bytes_req	= s->object_size;
-		__entry->bytes_alloc	= s->size;
+		__entry->bytes_req	= s ? s->object_size : 0;
+		__entry->bytes_alloc	= s ? s->size : 0;
 		__entry->gfp_flags	= (__force unsigned long)gfp_flags;
 		__entry->node		= node;
 		__entry->accounted	= IS_ENABLED(CONFIG_MEMCG_KMEM) ?
-- 
2.25.1