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>

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index d36702c7ab3c439413e48962828bf3efb2b511ad..88b34fdbf7592fd5e7a469cf9d84229b48557b1b 100644 (file)
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -529,6 +529,7 @@ 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;