linux-hardening - [PATCH v1 1/1] pstore/ram: Fix crash when setting number of cpus to an odd number

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Message-ID: <20230224023632.6840-1-weichen.chen@mediatek.com>
Date:   Fri, 24 Feb 2023 10:36:32 +0800
From:   Weichen Chen <weichen.chen@...iatek.com>
To:     <weichen.chen@...iatek.com>, <yt.shen@...iatek.com>,
        <darren.chen@...iatek.com>, <keescook@...omium.org>,
        <tony.luck@...el.com>, <angelogioacchino.delregno@...labora.com>,
        <matthias.bgg@...il.com>, <gpiccoli@...lia.com>,
        <linux-hardening@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v1 1/1] 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@...iatek.com>
---
 fs/pstore/ram.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index ade66dbe5f39..fc57ac97e506 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -528,6 +528,7 @@ static int ramoops_init_przs(const char *name,
 	}
 
 	zone_sz = mem_sz / *cnt;
+	zone_sz = ALIGN_DOWN(zone_sz, 2);
 	if (!zone_sz) {
 		dev_err(dev, "%s zone size == 0\n", name);
 		goto fail;
-- 
2.18.0