lkml.org 
[lkml]   [2019]   [Sep]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.19 42/79] ARM: 8874/1: mm: only adjust sections of valid mm structures
    Date
    From: Doug Berger <opendmb@gmail.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@gmail.com>
    Acked-by: Laura Abbott <labbott@redhat.com>
    Cc: Mike Rapoport <rppt@linux.ibm.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Florian Fainelli <f.fainelli@gmail.com>
    Cc: Rob Herring <robh@kernel.org>
    Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
    Cc: Peng Fan <peng.fan@nxp.com>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
    Signed-off-by: Sasha Levin <sashal@kernel.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 0cc8e04295a40..66b1568b95e05 100644
    --- a/arch/arm/mm/init.c
    +++ b/arch/arm/mm/init.c
    @@ -713,7 +713,8 @@ 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);
    }
    set_section_perms(perms, n, true, current->active_mm);
    set_section_perms(perms, n, true, &init_mm);
    --
    2.20.1


    \
     
     \ /
      Last update: 2019-09-20 00:32    [W:4.024 / U:0.056 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site