firmware: dmi: Fix unlikely out-of-bounds read in save_mem_devices
authorJean Delvare <jdelvare@suse.de>
Mon, 14 Oct 2019 19:41:24 +0000 (21:41 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 27 Jan 2020 13:51:19 +0000 (14:51 +0100)
[ Upstream commit 81dde26de9c08bb04c4962a15608778aaffb3cf9 ]

Before reading the Extended Size field, we should ensure it fits in
the DMI record. There is already a record length check but it does
not cover that field.

It would take a seriously corrupted DMI table to hit that bug, so no
need to worry, but we should still fix it.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Fixes: 6deae96b42eb ("firmware, DMI: Add function to look up a handle and return DIMM size")
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers/firmware/dmi_scan.c

index f248354..0dc0c78 100644 (file)
@@ -407,7 +407,7 @@ static void __init save_mem_devices(const struct dmi_header *dm, void *v)
                bytes = ~0ull;
        else if (size & 0x8000)
                bytes = (u64)(size & 0x7fff) << 10;
-       else if (size != 0x7fff)
+       else if (size != 0x7fff || dm->length < 0x20)
                bytes = (u64)size << 20;
        else
                bytes = (u64)get_unaligned((u32 *)&d[0x1C]) << 20;