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Message-Id: <20190919214759.795931660@linuxfoundation.org>
Date: Fri, 20 Sep 2019 00:04:22 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Doug Berger <opendmb@...il.com>,
Laura Abbott <labbott@...hat.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Florian Fainelli <f.fainelli@...il.com>,
Rob Herring <robh@...nel.org>,
"Steven Rostedt (VMware)" <rostedt@...dmis.org>,
Peng Fan <peng.fan@....com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Russell King <rmk+kernel@...linux.org.uk>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 41/56] ARM: 8874/1: mm: only adjust sections of valid mm structures
From: Doug Berger <opendmb@...il.com>
[ Upstream commit c51bc12d06b3a5494fbfcbd788a8e307932a06e9 ]
A timing hazard exists when an early fork/exec thread begins
exiting and sets its mm pointer to NULL while a separate core
tries to update the section information.
This commit ensures that the mm pointer is not NULL before
setting its section parameters. The arguments provided by
commit 11ce4b33aedc ("ARM: 8672/1: mm: remove tasklist locking
from update_sections_early()") are equally valid for not
requiring grabbing the task_lock around this check.
Fixes: 08925c2f124f ("ARM: 8464/1: Update all mm structures with section adjustments")
Signed-off-by: Doug Berger <opendmb@...il.com>
Acked-by: Laura Abbott <labbott@...hat.com>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Florian Fainelli <f.fainelli@...il.com>
Cc: Rob Herring <robh@...nel.org>
Cc: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Cc: Peng Fan <peng.fan@....com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
arch/arm/mm/init.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index a9f6705aea238..731b7e64715b9 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -691,7 +691,8 @@ static void update_sections_early(struct section_perm perms[], int n)
if (t->flags & PF_KTHREAD)
continue;
for_each_thread(t, s)
- set_section_perms(perms, n, true, s->mm);
+ if (s->mm)
+ set_section_perms(perms, n, true, s->mm);
}
read_unlock(&tasklist_lock);
set_section_perms(perms, n, true, current->active_mm);
--
2.20.1
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