Commit 8daf6df7 authored by Linus Walleij's avatar Linus Walleij Committed by Greg Kroah-Hartman
Browse files

ARM: 8978/1: mm: make act_mm() respect THREAD_SIZE

[ Upstream commit e1de9438


Recent work with KASan exposed the folling hard-coded bitmask
in arch/arm/mm/proc-macros.S:

  bic     rd, sp, #8128
  bic     rd, rd, #63

This forms the bitmask 0x1FFF that is coinciding with
(PAGE_SIZE << THREAD_SIZE_ORDER) - 1, this code was assuming
that THREAD_SIZE is always 8K (8192).

As KASan was increasing THREAD_SIZE_ORDER to 2, I ran into
this bug.

Fix it by this little oneline suggested by Ard:

  bic     rd, sp, #(THREAD_SIZE - 1) & ~63

Where THREAD_SIZE is defined using THREAD_SIZE_ORDER.

We have to also include <linux/const.h> since the THREAD_SIZE
expands to use the _AC() macro.

Cc: Ard Biesheuvel <>
Cc: Florian Fainelli <>
Suggested-by: default avatarArd Biesheuvel <>
Signed-off-by: default avatarLinus Walleij <>
Signed-off-by: default avatarRussell King <>
Signed-off-by: default avatarSasha Levin <>
parent 49b8ca65
......@@ -5,6 +5,7 @@
#include <linux/const.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
......@@ -30,7 +31,7 @@
* act_mm - get current->active_mm
.macro act_mm, rd
bic \rd, sp, #8128
bic \rd, sp, #(THREAD_SIZE - 1) & ~63
bic \rd, \rd, #63
ldr \rd, [\rd, #TI_TASK]
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