linux-kernel - [PATCH v5 1/2] m68k: process bootinfo records before saving them

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Message-Id: <20220927130835.1629806-1-Jason@zx2c4.com>
Date:   Tue, 27 Sep 2022 15:08:34 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH v5 1/2] m68k: process bootinfo records before saving them

The RNG seed boot record is memzeroed after processing, in order to
preserve forward secrecy. By saving the bootinfo for procfs prior to
that, forward secrecy is violated, since it becomes possible to recover
past states. So, save the bootinfo block only after first processing
them.

Fixes: a1ee38ab1a75 ("m68k: virt: Use RNG seed from bootinfo block")
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 arch/m68k/kernel/setup_mm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/kernel/setup_mm.c b/arch/m68k/kernel/setup_mm.c
index e62fa8f2149b..7e7ef67cff8b 100644
--- a/arch/m68k/kernel/setup_mm.c
+++ b/arch/m68k/kernel/setup_mm.c
@@ -109,10 +109,9 @@ extern void paging_init(void);
 
 static void __init m68k_parse_bootinfo(const struct bi_record *record)
 {
+	const struct bi_record *first_record = record;
 	uint16_t tag;
 
-	save_bootinfo(record);
-
 	while ((tag = be16_to_cpu(record->tag)) != BI_LAST) {
 		int unknown = 0;
 		const void *data = record->data;
@@ -182,6 +181,8 @@ static void __init m68k_parse_bootinfo(const struct bi_record *record)
 		record = (struct bi_record *)((unsigned long)record + size);
 	}
 
+	save_bootinfo(first_record);
+
 	m68k_realnum_memory = m68k_num_memory;
 #ifdef CONFIG_SINGLE_MEMORY_CHUNK
 	if (m68k_num_memory > 1) {
-- 
2.37.3