[PATCH v3 4/6] initramfs: Refactor to use hex2bin() instead of custom approach

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

There is a simple_strntoul() function used solely as a shortcut
for hex2bin() with proper endianess conversions. Replace that
and drop the unneeded function in the next changes.

This implementation will abort if we fail to parse the cpio header,
instead of using potentially bogus header values.

Co-developed-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 init/initramfs.c      | 44 +++++++++++++++++++++++++------------------
 init/initramfs_test.c | 23 ++++------------------
 2 files changed, 30 insertions(+), 37 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 4ed796566cf3..0d38ea8e63a2 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -6,6 +6,7 @@
 #include <linux/fcntl.h>
 #include <linux/file.h>
 #include <linux/fs.h>
+#include <linux/hex.h>
 #include <linux/init.h>
 #include <linux/init_syscalls.h>
 #include <linux/kstrtox.h>
@@ -21,6 +22,8 @@
 #include <linux/umh.h>
 #include <linux/utime.h>
 
+#include <asm/byteorder.h>
+
 #include "do_mounts.h"
 #include "initramfs_internal.h"
 
@@ -190,26 +193,30 @@ static __initdata gid_t gid;
 static __initdata unsigned rdev;
 static __initdata u32 hdr_csum;
 
-static void __init parse_header(char *s)
+static int __init parse_header(char *s)
 {
-	unsigned long parsed[13];
-	int i;
+	__be32 header[13];
+	int ret;
 
-	for (i = 0, s += 6; i < 13; i++, s += 8)
-		parsed[i] = simple_strntoul(s, NULL, 16, 8);
+	ret = hex2bin((u8 *)header, s + 6, sizeof(header));
+	if (ret) {
+		error("damaged header");
+		return ret;
+	}
 
-	ino = parsed[0];
-	mode = parsed[1];
-	uid = parsed[2];
-	gid = parsed[3];
-	nlink = parsed[4];
-	mtime = parsed[5]; /* breaks in y2106 */
-	body_len = parsed[6];
-	major = parsed[7];
-	minor = parsed[8];
-	rdev = new_encode_dev(MKDEV(parsed[9], parsed[10]));
-	name_len = parsed[11];
-	hdr_csum = parsed[12];
+	ino = be32_to_cpu(header[0]);
+	mode = be32_to_cpu(header[1]);
+	uid = be32_to_cpu(header[2]);
+	gid = be32_to_cpu(header[3]);
+	nlink = be32_to_cpu(header[4]);
+	mtime = be32_to_cpu(header[5]); /* breaks in y2106 */
+	body_len = be32_to_cpu(header[6]);
+	major = be32_to_cpu(header[7]);
+	minor = be32_to_cpu(header[8]);
+	rdev = new_encode_dev(MKDEV(be32_to_cpu(header[9]), be32_to_cpu(header[10])));
+	name_len = be32_to_cpu(header[11]);
+	hdr_csum = be32_to_cpu(header[12]);
+	return 0;
 }
 
 /* FSM */
@@ -289,7 +296,8 @@ static int __init do_header(void)
 			error("no cpio magic");
 		return 1;
 	}
-	parse_header(collected);
+	if (parse_header(collected))
+		return 1;
 	next_header = this_header + N_ALIGN(name_len) + body_len;
 	next_header = (next_header + 3) & ~3;
 	state = SkipIt;
diff --git a/init/initramfs_test.c b/init/initramfs_test.c
index 4d9a4075476c..df484f9d9c1b 100644
--- a/init/initramfs_test.c
+++ b/init/initramfs_test.c
@@ -499,8 +499,7 @@ static void __init initramfs_test_hdr_hex(struct kunit *test)
 {
 	char *err, *fmt;
 	size_t len;
-	struct kstat st0, st1;
-	char fdata[] = "this file data will be unpacked";
+	char fdata[] = "this file data will not be unpacked";
 	struct initramfs_test_bufs {
 		char cpio_src[(CPIO_HDRLEN + PATH_MAX + 3 + sizeof(fdata)) * 2];
 	} *tbufs = kzalloc(sizeof(struct initramfs_test_bufs), GFP_KERNEL);
@@ -528,28 +527,14 @@ static void __init initramfs_test_hdr_hex(struct kunit *test)
 	/*
 	 * override CPIO_HDR_FMT and instead use a format string which places
 	 * "0x" prefixes on the uid, gid and namesize values.
-	 * parse_header()/simple_str[n]toul() accept this.
+	 * parse_header()/simple_str[n]toul() accepted this, contrary to the
+	 * initramfs specification. hex2bin() now fails.
 	 */
 	fmt = "%s%08x%08x0x%06x0X%06x%08x%08x%08x%08x%08x%08x%08x0x%06x%08x%s";
 	len = fill_cpio(c, ARRAY_SIZE(c), fmt, tbufs->cpio_src);
 
 	err = unpack_to_rootfs(tbufs->cpio_src, len);
-	KUNIT_EXPECT_NULL(test, err);
-
-	KUNIT_EXPECT_EQ(test, init_stat(c[0].fname, &st0, 0), 0);
-	KUNIT_EXPECT_EQ(test, init_stat(c[1].fname, &st1, 0), 0);
-
-	KUNIT_EXPECT_TRUE(test,
-		uid_eq(st0.uid, make_kuid(current_user_ns(), (uid_t)0x123456)));
-	KUNIT_EXPECT_TRUE(test,
-		gid_eq(st0.gid, make_kgid(current_user_ns(), (gid_t)0x123457)));
-	KUNIT_EXPECT_TRUE(test,
-		uid_eq(st1.uid, make_kuid(current_user_ns(), (uid_t)0x56)));
-	KUNIT_EXPECT_TRUE(test,
-		gid_eq(st1.gid, make_kgid(current_user_ns(), (gid_t)0x57)));
-
-	KUNIT_EXPECT_EQ(test, init_unlink(c[0].fname), 0);
-	KUNIT_EXPECT_EQ(test, init_rmdir(c[1].fname), 0);
+	KUNIT_EXPECT_NOT_NULL(test, err);
 
 	kfree(tbufs);
 }
-- 
2.50.1