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@vger.kernel.org Fixes: d31e23aff011 ("ARM: mm: make vmalloc_seq handling SMP safe") Suggested-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Linus Walleij linus.walleij@linaro.org --- 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 =