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Draft: pstore/ram: Fix crash when setting number of cpus to an odd number

Lenny Szubowicz requested to merge lszubowi/centos-stream-9:rhel-29473 into main

JIRA: https://issues.redhat.com/browse/RHEL-29473
CVE: CVE-2023-52619

commit d49270a04623ce3c0afddbf3e984cb245aa48e9c
Author: Weichen Chen weichen.chen@mediatek.com
Date: Fri Feb 24 10:36:32 2023 +0800

pstore/ram: Fix crash when setting number of cpus to an odd number  

When the number of cpu cores is adjusted to 7 or other odd numbers,  
the zone size will become an odd number.  
The address of the zone will become:  
    addr of zone0 = BASE  
    addr of zone1 = BASE + zone_size  
    addr of zone2 = BASE + zone_size*2  
    ...  
The address of zone1/3/5/7 will be mapped to non-alignment va.  
Eventually crashes will occur when accessing these va.  

So, use ALIGN_DOWN() to make sure the zone size is even  
to avoid this bug.  

Signed-off-by: Weichen Chen <weichen.chen@mediatek.com>  
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>  
Tested-by: "Guilherme G. Piccoli" <gpiccoli@igalia.com>  
Link: https://lore.kernel.org/r/20230224023632.6840-1-weichen.chen@mediatek.com  
Signed-off-by: Kees Cook <keescook@chromium.org>

Signed-off-by: Lenny Szubowicz lszubowi@redhat.com

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