initramfs: don't free a non-existent initrd

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@arm.com
Fixes: 54c7a8916a88 ("initramfs: free initrd memory if opening /initrd.image fails")
Signed-off-by: Steven Price <steven.price@arm.com>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/init/initramfs.c b/init/initramfs.c
index 435a428..178130f 100644 (file)
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -669,7 +669,7 @@ done:
         * 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;