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

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 <ardb@kernel.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
alistair/sunxi64-5.8
Linus Walleij 2020-05-19 12:59:12 +01:00 committed by Russell King
parent fce2bc254a
commit e1de94380a
1 changed files with 2 additions and 1 deletions
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3
arch/arm/mm/proc-macros.S
View File

@ -5,6 +5,7 @@
* VMA_VM_FLAGS
* VM_EXEC
*/
#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]
.if (TSK_ACTIVE_MM > IMM12_MASK)