ARM: 9431/1: mm: Pair atomic_set_release() with _read_acquire()

BugLink: https://bugs.launchpad.net/bugs/2101915

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: d31e23aff0 ("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>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

This commit is contained in:

Linus Walleij

2025-03-11 08:51:19 +09:00

committed by

Stefan Bader

parent 6676873aac

commit 90bb96e4cc

1 changed files with 1 additions and 1 deletions

									
										arch/arm/mm/ioremap.c
									
		+1
		-1
	
												View File
												
				@@ -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 =