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

[Sasha Levin]

From: Weichen Chen <weichen.chen@xxxxxxxxxxxx>

[ 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@xxxxxxxxxxxx>
Reviewed-by: Matthias Brugger <matthias.bgg@xxxxxxxxx>
Tested-by: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230224023632.6840-1-weichen.chen@xxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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