initramfs: support cpio extraction with file checksums

Add support for extraction of checksum-enabled "070702" cpio archives,
specified in Documentation/driver-api/early-userspace/buffer-format.rst.
Fail extraction if the calculated file data checksum doesn't match the
value carried in the header.

Link: https://lkml.kernel.org/r/20220404093429.27570-7-ddiss@suse.de
Signed-off-by: David Disseldorp <ddiss@suse.de>
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Martin Wilck <mwilck@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/init/initramfs.c b/init/initramfs.c
index b5bfed8..dc84cf7 100644 (file)
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -17,8 +17,11 @@
 #include <linux/init_syscalls.h>
 #include <linux/umh.h>
 
-static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
-               loff_t *pos)
+static __initdata bool csum_present;
+static __initdata u32 io_csum;
+
+static ssize_t __init xwrite(struct file *file, const unsigned char *p,
+               size_t count, loff_t *pos)
 {
        ssize_t out = 0;
 
@@ -33,6 +36,13 @@ static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
                } else if (rv == 0)
                        break;
 
+               if (csum_present) {
+                       ssize_t i;
+
+                       for (i = 0; i < rv; i++)
+                               io_csum += p[i];
+               }
+
                p += rv;
                out += rv;
                count -= rv;
@@ -176,15 +186,16 @@ static __initdata unsigned long body_len, name_len;
 static __initdata uid_t uid;
 static __initdata gid_t gid;
 static __initdata unsigned rdev;
+static __initdata u32 hdr_csum;
 
 static void __init parse_header(char *s)
 {
-       unsigned long parsed[12];
+       unsigned long parsed[13];
        char buf[9];
        int i;
 
        buf[8] = '\0';
-       for (i = 0, s += 6; i < 12; i++, s += 8) {
+       for (i = 0, s += 6; i < 13; i++, s += 8) {
                memcpy(buf, s, 8);
                parsed[i] = simple_strtoul(buf, NULL, 16);
        }
@@ -199,6 +210,7 @@ static void __init parse_header(char *s)
        minor = parsed[8];
        rdev = new_encode_dev(MKDEV(parsed[9], parsed[10]));
        name_len = parsed[11];
+       hdr_csum = parsed[12];
 }
 
 /* FSM */
@@ -267,7 +279,11 @@ static int __init do_collect(void)
 
 static int __init do_header(void)
 {
-       if (memcmp(collected, "070701", 6)) {
+       if (!memcmp(collected, "070701", 6)) {
+               csum_present = false;
+       } else if (!memcmp(collected, "070702", 6)) {
+               csum_present = true;
+       } else {
                if (memcmp(collected, "070707", 6) == 0)
                        error("incorrect cpio method used: use -H newc option");
                else
@@ -362,6 +378,7 @@ static int __init do_name(void)
                        if (IS_ERR(wfile))
                                return 0;
                        wfile_pos = 0;
+                       io_csum = 0;
 
                        vfs_fchown(wfile, uid, gid);
                        vfs_fchmod(wfile, mode);
@@ -394,6 +411,8 @@ static int __init do_copy(void)
 
                do_utime_path(&wfile->f_path, mtime);
                fput(wfile);
+               if (csum_present && io_csum != hdr_csum)
+                       error("bad data checksum");
                eat(body_len);
                state = SkipIt;
                return 0;