6.6-stable review patch. If anyone has any objections, please let me know.
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From: Linus Walleij linus.walleij@linaro.org
commit 93ee385254d53849c01dd8ab9bc9d02790ee7f0e upstream.
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 Signed-off-by: Russell King (Oracle) rmk+kernel@armlinux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/mm/ioremap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm/mm/ioremap.c +++ b/arch/arm/mm/ioremap.c @@ -141,7 +141,7 @@ void __check_vmalloc_seq(struct mm_struc 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 =