The code for syncing vmalloc memory PGD pointers is using
atomic_read() in pair with atomic_set_release() but the
proper pairing is atomic_read_acquire() paired with
atomic_set_release().
This is done to clearly instruct the compiler to not
reorder the memcpy() or similar calls inside the section
so that we do not observe changes to init_mm. memcpy()
calls should be identified by the compiler as having
unpredictable side effects, but let's try to be on the
safe side.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: d31e23aff011 ("ARM: mm: make vmalloc_seq handling SMP safe")
Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
arch/arm/mm/ioremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index ff555823cceb..89f1c97f3079 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -141,7 +141,7 @@ void __check_vmalloc_seq(struct mm_struct *mm)
int seq;
do {
- seq = atomic_read(&init_mm.context.vmalloc_seq);
+ seq = atomic_read_acquire(&init_mm.context.vmalloc_seq);
memcpy_pgd(mm, VMALLOC_START, VMALLOC_END);
if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
unsigned long start =
--
2.46.2
