From 4ff1ddae358dff002080d753e45721a89d07b3af Mon Sep 17 00:00:00 2001 From: P J P Date: Sun, 15 Sep 2013 13:03:17 +0530 Subject: [PATCH 1/2] NULL pointer dereference while loading initramfs Make menuconfig allows one to choose compression format of an initial ramdisk image. But this choice does not result in duly compressed initial ramdisk image. Because - $ make install - does not pass on the selected compression choice to the dracut(8) tool, which creates the initramfs file. dracut(8) generates the image with the default compression, ie. gzip(1). If a user chose any other compression instead of gzip(1), it leads to a crash due to NULL pointer dereference in crd_load(), caused by a NULL function pointer returned by the 'decompress_method()' routine. Because the initramfs image is gzip(1) compressed, whereas the kernel knows how decompress the chosen format and not gzip(1). This patch replaces the crash by an explicit panic() call with an appropriate error message. This shall prevent the kernel from eventually panicking in: init/do_mounts.c: mount_block_root() with -> panic("VFS: Unable to mount root fs on %s", b); Signed-off-by: P J P diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c index 6be2879..76faec1 100644 --- a/init/do_mounts_rd.c +++ b/init/do_mounts_rd.c @@ -342,6 +342,13 @@ static int __init crd_load(int in_fd, int out_fd, decompress_fn deco) int result; crd_infd = in_fd; crd_outfd = out_fd; + + if (!deco) + { + printk(KERN_EMERG "Invalid decompression routine address: %p\n", deco); + panic("Could not decompress initial ramdisk image."); + } + result = deco(NULL, 0, compr_fill, compr_flush, NULL, NULL, error); if (decompress_error) result = 1; -- 1.8.3.1