[PATCH 4.19 47/63] initramfs: dont free a non-existent initrd

[Greg Kroah-Hartman]

From: Steven Price <steven.price@xxxxxxx>

[ Upstream commit 5d59aa8f9ce972b472201aed86e904bb75879ff0 ]

Since commit 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.

Link: http://lkml.kernel.org/r/20190516143125.48948-1-steven.price@xxxxxxx
Fixes: 54c7a8916a88 ("initramfs: free initrd memory if opening /initrd.image fails")
Signed-off-by: Steven Price <steven.price@xxxxxxx>
Reported-by: Mark Rutland <mark.rutland@xxxxxxx>
Tested-by: Mark Rutland <mark.rutland@xxxxxxx>
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 init/initramfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index cd5fb00fcb549..dab8d63459f63 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -524,7 +524,7 @@ static void __init free_initrd(void)
 	unsigned long crashk_start = (unsigned long)__va(crashk_res.start);
 	unsigned long crashk_end   = (unsigned long)__va(crashk_res.end);
 #endif
-	if (do_retain_initrd)
+	if (do_retain_initrd || !initrd_start)
 		goto skip;
 
 #ifdef CONFIG_KEXEC_CORE
-- 
2.20.1