linux-kernel - [PATCH] initramfs: Don't free a non-existent initrd

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Message-Id: <20190516143125.48948-1-steven.price@arm.com>
Date:   Thu, 16 May 2019 15:31:25 +0100
From:   Steven Price <steven.price@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org,
        Steven Price <steven.price@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH] initramfs: Don't free a non-existent initrd

Since 54c7a8916a88 ("initramfs: free initrd memory if opening
/initrd.image fails"), the kernel has unconditionally attempted to free
the initrd even if it doesn't exist. In the non-existent case this
causes a boot-time splat if CONFIG_DEBUG_VIRTUAL is enabled due to a
call to virt_to_phys() with a NULL address.

Instead we should check that the initrd actually exists and only attempt
to free it if it does.

Fixes: 54c7a8916a88 ("initramfs: free initrd memory if opening /initrd.image fails")
Reported-by: Mark Rutland <mark.rutland@....com>
Tested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Steven Price <steven.price@....com>
---
 init/initramfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 435a428c2af1..178130fd61c2 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -669,7 +669,7 @@ static int __init populate_rootfs(void)
 	 * If the initrd region is overlapped with crashkernel reserved region,
 	 * free only memory that is not part of crashkernel region.
 	 */
-	if (!do_retain_initrd && !kexec_free_initrd())
+	if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
 		free_initrd_mem(initrd_start, initrd_end);
 	initrd_start = 0;
 	initrd_end = 0;
-- 
2.20.1