Merge tag 'vfs-6.15-rc1.initramfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs initramfs updates from Christian Brauner:
 "This adds basic kunit test coverage for initramfs unpacking and cleans
  up some buffer handling issues and inefficiencies"

* tag 'vfs-6.15-rc1.initramfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  MAINTAINERS: append initramfs files to the VFS section
  initramfs: avoid static buffer for error message
  initramfs: fix hardlink hash leak without TRAILER
  initramfs: reuse name_len for dir mtime tracking
  initramfs: allocate heap buffers together
  initramfs: avoid memcpy for hex header fields
  vsprintf: add simple_strntoul
  initramfs_test: kunit tests for initramfs unpacking
  init: add initramfs_internal.h

Author: torvalds

MAINTAINERS

@@ -8903,6 +8903,9 @@ F:	include/linux/fs.h
 F:	include/linux/fs_types.h
 F:	include/uapi/linux/fs.h
 F:	include/uapi/linux/openat2.h
+F:	Documentation/driver-api/early-userspace/buffer-format.rst
+F:	init/do_mounts*
+F:	init/*initramfs*
 
 FILESYSTEMS [EXPORTFS]
 M:	Chuck Lever <chuck.lever@oracle.com>

include/linux/kstrtox.h

@@ -143,6 +143,7 @@ static inline int __must_check kstrtos32_from_user(const char __user *s, size_t
  */
 
 extern unsigned long simple_strtoul(const char *,char **,unsigned int);
+extern unsigned long simple_strntoul(const char *,char **,unsigned int,size_t);
 extern long simple_strtol(const char *,char **,unsigned int);
 extern unsigned long long simple_strtoull(const char *,char **,unsigned int);
 extern long long simple_strtoll(const char *,char **,unsigned int);

init/.kunitconfig

@@ -0,0 +1,3 @@
+CONFIG_KUNIT=y
+CONFIG_BLK_DEV_INITRD=y
+CONFIG_INITRAMFS_TEST=y

init/Kconfig

@@ -1454,6 +1454,13 @@ config INITRAMFS_PRESERVE_MTIME
 
 	  If unsure, say Y.
 
+config INITRAMFS_TEST
+	bool "Test initramfs cpio archive extraction" if !KUNIT_ALL_TESTS
+	depends on BLK_DEV_INITRD && KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  Build KUnit tests for initramfs. See Documentation/dev-tools/kunit
+
 choice
 	prompt "Compiler optimization level"
 	default CC_OPTIMIZE_FOR_PERFORMANCE

init/Makefile

@@ -12,6 +12,7 @@ else
 obj-$(CONFIG_BLK_DEV_INITRD)   += initramfs.o
 endif
 obj-$(CONFIG_GENERIC_CALIBRATE_DELAY) += calibrate.o
+obj-$(CONFIG_INITRAMFS_TEST)   += initramfs_test.o
 
 obj-y                          += init_task.o
 

init/initramfs.c

@@ -20,6 +20,7 @@
 #include <linux/security.h>
 
 #include "do_mounts.h"
+#include "initramfs_internal.h"
 
 static __initdata bool csum_present;
 static __initdata u32 io_csum;
@@ -75,6 +76,7 @@ static __initdata struct hash {
 	struct hash *next;
 	char name[N_ALIGN(PATH_MAX)];
 } *head[32];
+static __initdata bool hardlink_seen;
 
 static inline int hash(int major, int minor, int ino)
 {
@@ -108,19 +110,21 @@ static char __init *find_link(int major, int minor, int ino,
 	strcpy(q->name, name);
 	q->next = NULL;
 	*p = q;
+	hardlink_seen = true;
 	return NULL;
 }
 
 static void __init free_hash(void)
 {
 	struct hash **p, *q;
-	for (p = head; p < head + 32; p++) {
+	for (p = head; hardlink_seen && p < head + 32; p++) {
 		while (*p) {
 			q = *p;
 			*p = q->next;
 			kfree(q);
 		}
 	}
+	hardlink_seen = false;
 }
 
 #ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
@@ -143,9 +147,8 @@ struct dir_entry {
 	char name[];
 };
 
-static void __init dir_add(const char *name, time64_t mtime)
+static void __init dir_add(const char *name, size_t nlen, time64_t mtime)
 {
-	size_t nlen = strlen(name) + 1;
 	struct dir_entry *de;
 
 	de = kmalloc(sizeof(struct dir_entry) + nlen, GFP_KERNEL);
@@ -169,7 +172,7 @@ static void __init dir_utime(void)
 #else
 static void __init do_utime(char *filename, time64_t mtime) {}
 static void __init do_utime_path(const struct path *path, time64_t mtime) {}
-static void __init dir_add(const char *name, time64_t mtime) {}
+static void __init dir_add(const char *name, size_t nlen, time64_t mtime) {}
 static void __init dir_utime(void) {}
 #endif
 
@@ -188,14 +191,11 @@ static __initdata u32 hdr_csum;
 static void __init parse_header(char *s)
 {
 	unsigned long parsed[13];
-	char buf[9];
 	int i;
 
-	buf[8] = '\0';
-	for (i = 0, s += 6; i < 13; i++, s += 8) {
-		memcpy(buf, s, 8);
-		parsed[i] = simple_strtoul(buf, NULL, 16);
-	}
+	for (i = 0, s += 6; i < 13; i++, s += 8)
+		parsed[i] = simple_strntoul(s, NULL, 16, 8);
+
 	ino = parsed[0];
 	mode = parsed[1];
 	uid = parsed[2];
@@ -256,7 +256,7 @@ static __initdata char *header_buf, *symlink_buf, *name_buf;
 
 static int __init do_start(void)
 {
-	read_into(header_buf, 110, GotHeader);
+	read_into(header_buf, CPIO_HDRLEN, GotHeader);
 	return 0;
 }
 
@@ -396,7 +396,7 @@ static int __init do_name(void)
 		init_mkdir(collected, mode);
 		init_chown(collected, uid, gid, 0);
 		init_chmod(collected, mode);
-		dir_add(collected, mtime);
+		dir_add(collected, name_len, mtime);
 	} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
 		   S_ISFIFO(mode) || S_ISSOCK(mode)) {
 		if (maybe_link() == 0) {
@@ -497,20 +497,33 @@ static unsigned long my_inptr __initdata; /* index of next byte to be processed
 
 #include <linux/decompress/generic.h>
 
-static char * __init unpack_to_rootfs(char *buf, unsigned long len)
+/**
+ * unpack_to_rootfs - decompress and extract an initramfs archive
+ * @buf: input initramfs archive to extract
+ * @len: length of initramfs data to process
+ *
+ * Returns: NULL for success or an error message string
+ *
+ * This symbol shouldn't be used externally. It's available for unit tests.
+ */
+char * __init unpack_to_rootfs(char *buf, unsigned long len)
 {
 	long written;
 	decompress_fn decompress;
 	const char *compress_name;
-	static __initdata char msg_buf[64];
+	struct {
+		char header[CPIO_HDRLEN];
+		char symlink[PATH_MAX + N_ALIGN(PATH_MAX) + 1];
+		char name[N_ALIGN(PATH_MAX)];
+	} *bufs = kmalloc(sizeof(*bufs), GFP_KERNEL);
 
-	header_buf = kmalloc(110, GFP_KERNEL);
-	symlink_buf = kmalloc(PATH_MAX + N_ALIGN(PATH_MAX) + 1, GFP_KERNEL);
-	name_buf = kmalloc(N_ALIGN(PATH_MAX), GFP_KERNEL);
-
-	if (!header_buf || !symlink_buf || !name_buf)
+	if (!bufs)
 		panic_show_mem("can't allocate buffers");
 
+	header_buf = bufs->header;
+	symlink_buf = bufs->symlink;
+	name_buf = bufs->name;
+
 	state = Start;
 	this_header = 0;
 	message = NULL;
@@ -538,12 +551,9 @@ static char * __init unpack_to_rootfs(char *buf, unsigned long len)
 			if (res)
 				error("decompressor failed");
 		} else if (compress_name) {
-			if (!message) {
-				snprintf(msg_buf, sizeof msg_buf,
-					 "compression method %s not configured",
-					 compress_name);
-				message = msg_buf;
-			}
+			pr_err("compression method %s not configured\n",
+			       compress_name);
+			error("decompressor failed");
 		} else
 			error("invalid magic at start of compressed archive");
 		if (state != Reset)
@@ -553,9 +563,9 @@ static char * __init unpack_to_rootfs(char *buf, unsigned long len)
 		len -= my_inptr;
 	}
 	dir_utime();
-	kfree(name_buf);
-	kfree(symlink_buf);
-	kfree(header_buf);
+	/* free any hardlink state collected without optional TRAILER!!! */
+	free_hash();
+	kfree(bufs);
 	return message;
 }
 

init/initramfs_internal.h

@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef __INITRAMFS_INTERNAL_H__
+#define __INITRAMFS_INTERNAL_H__
+
+char *unpack_to_rootfs(char *buf, unsigned long len);
+#define CPIO_HDRLEN 110
+
+#endif