linux-hardening - [PATCH AUTOSEL 5.15 07/13] pstore/ram: Fix crash when setting number of cpus to an odd number

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Message-ID: <20240116002603.215942-7-sashal@kernel.org>
Date: Mon, 15 Jan 2024 19:25:43 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Weichen Chen <weichen.chen@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	Kees Cook <keescook@...omium.org>,
	Sasha Levin <sashal@...nel.org>,
	angelogioacchino.delregno@...labora.com,
	linux-hardening@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.15 07/13] pstore/ram: Fix crash when setting number of cpus to an odd number

From: Weichen Chen <weichen.chen@...iatek.com>

[ Upstream commit d49270a04623ce3c0afddbf3e984cb245aa48e9c ]

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>
Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>
Tested-by: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Link: https://lore.kernel.org/r/20230224023632.6840-1-weichen.chen@mediatek.com
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/pstore/ram.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index f3fa3625d772..e15b4631364a 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -519,6 +519,7 @@ 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;
-- 
2.43.0