From: Linus Walleij <linus.walleij@linaro.org>
To: Russell King <linux@armlinux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Florian Fainelli <f.fainelli@gmail.com>,
Ard Biesheuvel <ardb@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: mm: make act_mm() respect THREAD_SIZE_ORDER
Date: Thu, 14 May 2020 15:57:37 +0200 [thread overview]
Message-ID: <20200514135737.309146-1-linus.walleij@linaro.org> (raw)
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, #(4095 << THREAD_SIZE_ORDER) & ~63
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>
---
I'm sending this as a separate preparatory fix as it is
a nice fix in its own right. I am now testing KASan on
ARMv4 and ARMv5 and with some minimal busybox userspace
it is quite possible to run it on even really small
devices like the Gemini-based routers and NAS from
D-Link.
---
arch/arm/mm/proc-macros.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index 5461d589a1e2..ba100b2d0ac2 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -30,7 +30,7 @@
* act_mm - get current->active_mm
*/
.macro act_mm, rd
- bic \rd, sp, #8128
+ bic \rd, sp, #(4095 << THREAD_SIZE_ORDER) & ~63
bic \rd, \rd, #63
ldr \rd, [\rd, #TI_TASK]
.if (TSK_ACTIVE_MM > IMM12_MASK)
--
2.25.4
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2020-05-14 14:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-14 13:57 Linus Walleij [this message]
2020-05-14 17:19 ` [PATCH] ARM: mm: make act_mm() respect THREAD_SIZE_ORDER Ard Biesheuvel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200514135737.309146-1-linus.walleij@linaro.org \
--to=linus.walleij@linaro.org \
--cc=ardb@kernel.org \
--cc=f.fainelli@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux@armlinux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.