[PATCH] kexec: fix in free initrd when overlapped with crashkernel region

It is possible that the reserved crashkernel region can be overlapped with
initrd since the bootloader sets the initrd location.  When the initrd
region is freed, the second kernel memory will not be contiguous.  The
Kexec_load can cause an oops since there is no contiguous memory to write
the second kernel or this memory could be used in the first kernel itself
and may not be part of the dump.  For example, on powerpc, the initrd is
located at 36MB and the crashkernel starts at 32MB.  The kexec_load caused
panic since writing into non-allocated memory (after 36MB).  We could see
the similar issue even on other archs.

One possibility is to move the initrd outside of crashkernel region.  But,
the initrd region will be freed anyway before the system is up.  This patch
fixes this issue and frees only regions that are not part of crashkernel
memory in case overlaps.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/kexec.h

@@ -6,6 +6,7 @@
 #include <linux/list.h>
 #include <linux/linkage.h>
 #include <linux/compat.h>
+#include <linux/ioport.h>
 #include <asm/kexec.h>
 
 /* Verify architecture specific macros are defined */

init/initramfs.c

@@ -466,10 +466,32 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len, int check_only)
 extern char __initramfs_start[], __initramfs_end[];
 #ifdef CONFIG_BLK_DEV_INITRD
 #include <linux/initrd.h>
+#include <linux/kexec.h>
 
 static void __init free_initrd(void)
 {
-	free_initrd_mem(initrd_start, initrd_end);
+#ifdef CONFIG_KEXEC
+	unsigned long crashk_start = (unsigned long)__va(crashk_res.start);
+	unsigned long crashk_end   = (unsigned long)__va(crashk_res.end);
+
+	/*
+	 * If the initrd region is overlapped with crashkernel reserved region,
+	 * free only memory that is not part of crashkernel region.
+	 */
+	if (initrd_start < crashk_end && initrd_end > crashk_start) {
+		/*
+		 * Initialize initrd memory region since the kexec boot does
+		 * not do.
+		 */
+		memset((void *)initrd_start, 0, initrd_end - initrd_start);
+		if (initrd_start < crashk_start)
+			free_initrd_mem(initrd_start, crashk_start);
+		if (initrd_end > crashk_end)
+			free_initrd_mem(crashk_end, initrd_end);
+	} else
+#endif
+		free_initrd_mem(initrd_start, initrd_end);
+
 	initrd_start = 0;
 	initrd_end = 0;
 }