On 07.11.24 12:34, Qiu-ji Chen wrote:
The function call alloc_percpu() returns a pointer to the memory address,
but it hasn't been checked. Our static analysis tool indicates that null
pointer dereference may exist in pointer zone->per_cpu_pageset. It is
always safe to judge the null pointer before use.
Signed-off-by: Qiu-ji Chen <chenqiuji666@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 9420f89db2dd ("mm: move most of core MM initialization to mm/mm_init.c")
---
mm/page_alloc.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8afab64814dc..5deae1193dc3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5703,8 +5703,14 @@ void __meminit setup_zone_pageset(struct zone *zone)
/* Size may be 0 on !SMP && !NUMA */
if (sizeof(struct per_cpu_zonestat) > 0)
zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
+ if (!zone->per_cpu_pageset)
+ return;
Don't we initialize this for all with &boot_pageset? How could this ever
happen?
zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
+ if (!zone->per_cpu_pageset) {
+ free_percpu(zone->per_cpu_pageset);
+ return;
If it's NULL, we free it. Why?
+ }
for_each_possible_cpu(cpu) {
struct per_cpu_pages *pcp;
struct per_cpu_zonestat *pzstats;
Also, how could core code ever recover if this function would return
early, leaving something partially initialized?
The missing NULL check is concerning, but looking into alloc_percpu() we
treat these as atomic allocations and would print a warning in case this
would ever happen. So likely it never really happens in practice.
I wonder if we simply want to leave it unmodified (IOW set to
&boot_pageset) in case the allocation fails. We'd already print a
warning in this unexpected scenario.
--
Cheers,
David / dhildenb
