initramfs: "crc" cpio format and INITRAMFS_PRESERVE_MTIME

initramfs: "crc" cpio format and INITRAMFS_PRESERVE_MTIME

[David Disseldorp]

This patchset does some minor initramfs refactoring and allows cpio
entry mtime preservation to be disabled via a new Kconfig
INITRAMFS_PRESERVE_MTIME option.
Patches 3/5 to 5/5 implement support for creation and extraction of
"crc" cpio archives, which carry file data checksums. Basic tests for
this functionality can be found at
Link: https://github.com/rapido-linux/rapido/pull/163

Changes since v4, following feedback from Matthew Wilcox:
- implement cpio "crc" archive creation and extraction
- add patch to fix gen_init_cpio short read handling
- drop now-unnecessary "crc" documentation and error msg changes

Changes since v3, following feedback from Martin Wilck:
- 4/4: keep vfs_utimes() call in do_copy() path
  + drop [PATCH v3 4/5] initramfs: use do_utime() wrapper consistently
  + add do_utime_path() helper
  + clean up timespec64 initialisation
- 4/4: move all mtime preservation logic to initramfs_mtime.h and drop
  separate .c
- 4/4: improve commit message


 init/Kconfig           | 10 +++++
 init/initramfs.c       | 89 +++++++++++++++-------------------------
 init/initramfs_mtime.h | 50 +++++++++++++++++++++++
 usr/gen_init_cpio.c    | 92 ++++++++++++++++++++++++++++++------------
 4 files changed, 159 insertions(+), 82 deletions(-)

[PATCH v5 1/5] initramfs: refactor do_header() cpio magic checks

[David Disseldorp]

do_header() is called for each cpio entry and fails if the first six
bytes don't match "newc" magic. The magic check includes a special case
error message if POSIX.1 ASCII (cpio -H odc) magic is detected. This
special case POSIX.1 check can be nested under the "newc" mismatch code
path to avoid calling memcmp() twice in a non-error case.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Martin Wilck <mwilck@suse.com>
---
 init/initramfs.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 2f3d96dc3db6..2f79b3ec0b40 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -257,12 +257,11 @@ static int __init do_collect(void)
 
 static int __init do_header(void)
 {
-	if (memcmp(collected, "070707", 6)==0) {
-		error("incorrect cpio method used: use -H newc option");
-		return 1;
-	}
 	if (memcmp(collected, "070701", 6)) {
-		error("no cpio magic");
+		if (memcmp(collected, "070707", 6) == 0)
+			error("incorrect cpio method used: use -H newc option");
+		else
+			error("no cpio magic");
 		return 1;
 	}
 	parse_header(collected);
-- 
2.31.1

[PATCH v5 2/5] initramfs: add INITRAMFS_PRESERVE_MTIME Kconfig option

[David Disseldorp]

initramfs cpio mtime preservation, as implemented in commit 889d51a10712
("initramfs: add option to preserve mtime from initramfs cpio images"),
uses a linked list to defer directory mtime processing until after all
other items in the cpio archive have been processed. This is done to
ensure that parent directory mtimes aren't overwritten via subsequent
child creation. Contrary to the 889d51a10712 commit message, the mtime
preservation behaviour is unconditional.

This change adds a new INITRAMFS_PRESERVE_MTIME Kconfig option, which
can be used to disable on-by-default mtime retention and in turn
speed up initramfs extraction, particularly for cpio archives with large
directory counts.

Benchmarks with a one million directory cpio archive extracted 20 times
demonstrated:
				mean extraction time (s)	std dev
INITRAMFS_PRESERVE_MTIME=y		3.808			 0.006
INITRAMFS_PRESERVE_MTIME unset		3.056			 0.004

The above extraction times were measured using ftrace
(initcall_finish - initcall_start) values for populate_rootfs() with
initramfs_async disabled.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Martin Wilck <mwilck@suse.com>
---
 init/Kconfig           | 10 +++++++++
 init/initramfs.c       | 48 +++-------------------------------------
 init/initramfs_mtime.h | 50 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 45 deletions(-)
 create mode 100644 init/initramfs_mtime.h

diff --git a/init/Kconfig b/init/Kconfig
index 4b7bac10c72d..a98f63d3c366 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1357,6 +1357,16 @@ config BOOT_CONFIG
 
 	  If unsure, say Y.
 
+config INITRAMFS_PRESERVE_MTIME
+	bool "Preserve cpio archive mtimes in initramfs"
+	default y
+	help
+	  Each entry in an initramfs cpio archive carries an mtime value. When
+	  enabled, extracted cpio items take this mtime, with directory mtime
+	  setting deferred until after creation of any child entries.
+
+	  If unsure, say Y.
+
 choice
 	prompt "Compiler optimization level"
 	default CC_OPTIMIZE_FOR_PERFORMANCE
diff --git a/init/initramfs.c b/init/initramfs.c
index 2f79b3ec0b40..5b4ca8ecadb5 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -17,6 +17,8 @@
 #include <linux/init_syscalls.h>
 #include <linux/umh.h>
 
+#include "initramfs_mtime.h"
+
 static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
 		loff_t *pos)
 {
@@ -116,46 +118,6 @@ static void __init free_hash(void)
 	}
 }
 
-static long __init do_utime(char *filename, time64_t mtime)
-{
-	struct timespec64 t[2];
-
-	t[0].tv_sec = mtime;
-	t[0].tv_nsec = 0;
-	t[1].tv_sec = mtime;
-	t[1].tv_nsec = 0;
-	return init_utimes(filename, t);
-}
-
-static __initdata LIST_HEAD(dir_list);
-struct dir_entry {
-	struct list_head list;
-	char *name;
-	time64_t mtime;
-};
-
-static void __init dir_add(const char *name, time64_t mtime)
-{
-	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
-	if (!de)
-		panic_show_mem("can't allocate dir_entry buffer");
-	INIT_LIST_HEAD(&de->list);
-	de->name = kstrdup(name, GFP_KERNEL);
-	de->mtime = mtime;
-	list_add(&de->list, &dir_list);
-}
-
-static void __init dir_utime(void)
-{
-	struct dir_entry *de, *tmp;
-	list_for_each_entry_safe(de, tmp, &dir_list, list) {
-		list_del(&de->list);
-		do_utime(de->name, de->mtime);
-		kfree(de->name);
-		kfree(de);
-	}
-}
-
 static __initdata time64_t mtime;
 
 /* cpio header parsing */
@@ -379,14 +341,10 @@ static int __init do_name(void)
 static int __init do_copy(void)
 {
 	if (byte_count >= body_len) {
-		struct timespec64 t[2] = { };
 		if (xwrite(wfile, victim, body_len, &wfile_pos) != body_len)
 			error("write error");
 
-		t[0].tv_sec = mtime;
-		t[1].tv_sec = mtime;
-		vfs_utimes(&wfile->f_path, t);
-
+		do_utime_path(&wfile->f_path, mtime);
 		fput(wfile);
 		eat(body_len);
 		state = SkipIt;
diff --git a/init/initramfs_mtime.h b/init/initramfs_mtime.h
new file mode 100644
index 000000000000..fbd8757b34a9
--- /dev/null
+++ b/init/initramfs_mtime.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
+static void __init do_utime(char *filename, time64_t mtime)
+{
+	struct timespec64 t[2] = { { .tv_sec = mtime }, { .tv_sec = mtime } };
+	init_utimes(filename, t);
+}
+
+static void __init do_utime_path(const struct path *path, time64_t mtime)
+{
+	struct timespec64 t[2] = { { .tv_sec = mtime }, { .tv_sec = mtime } };
+	vfs_utimes(path, t);
+}
+
+static __initdata LIST_HEAD(dir_list);
+struct dir_entry {
+	struct list_head list;
+	char *name;
+	time64_t mtime;
+};
+
+static void __init dir_add(const char *name, time64_t mtime)
+{
+	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
+	if (!de)
+		panic("can't allocate dir_entry buffer");
+	INIT_LIST_HEAD(&de->list);
+	de->name = kstrdup(name, GFP_KERNEL);
+	de->mtime = mtime;
+	list_add(&de->list, &dir_list);
+}
+
+static void __init dir_utime(void)
+{
+	struct dir_entry *de, *tmp;
+
+	list_for_each_entry_safe(de, tmp, &dir_list, list) {
+		list_del(&de->list);
+		do_utime(de->name, de->mtime);
+		kfree(de->name);
+		kfree(de);
+	}
+}
+#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_utime(void) {}
+#endif
-- 
2.31.1

Re: [PATCH v5 2/5] initramfs: add INITRAMFS_PRESERVE_MTIME Kconfig option

[David Disseldorp]

On Tue, 14 Dec 2021 00:20:05 +0100, David Disseldorp wrote:

> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -17,6 +17,8 @@
...
> -static void __init dir_add(const char *name, time64_t mtime)
> -{
> -	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
> -	if (!de)
> -		panic_show_mem("can't allocate dir_entry buffer");
> -	INIT_LIST_HEAD(&de->list);
> -	de->name = kstrdup(name, GFP_KERNEL);
> -	de->mtime = mtime;
> -	list_add(&de->list, &dir_list);
> -}
...
> --- /dev/null
> +++ b/init/initramfs_mtime.h
...
> +static void __init dir_add(const char *name, time64_t mtime)
> +{
> +	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
> +	if (!de)
> +		panic("can't allocate dir_entry buffer");
> +	INIT_LIST_HEAD(&de->list);
> +	de->name = kstrdup(name, GFP_KERNEL);
> +	de->mtime = mtime;
> +	list_add(&de->list, &dir_list);
> +}

I might as well fix the unhandled kstrdup() failure, rather than copying
it here. I'll post another round which allocates the "name" buffer via
the dir_entry kmalloc() call.

[PATCH v5 3/5] gen_init_cpio: fix short read file handling

[David Disseldorp]

When processing a "file" entry, gen_init_cpio attempts to allocate a
buffer large enough to stage the entire contents of the source file.
It then attempts to fill the buffer via a single read() call and
subsequently writes out the entire buffer length, without checking that
read() returned the full length, potentially writing uninitialized
buffer memory.

Fix this by breaking up file I/O into 64k chunks and only writing the
length returned by the prior read() call.

Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 usr/gen_init_cpio.c | 44 +++++++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
index 0e2c8a5838b1..9a0f8c37273a 100644
--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -20,6 +20,7 @@
 
 #define xstr(s) #s
 #define str(s) xstr(s)
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
 
 static unsigned int offset;
 static unsigned int ino = 721;
@@ -297,9 +298,8 @@ static int cpio_mkfile(const char *name, const char *location,
 			unsigned int nlinks)
 {
 	char s[256];
-	char *filebuf = NULL;
 	struct stat buf;
-	long size;
+	unsigned long size;
 	int file = -1;
 	int retval;
 	int rc = -1;
@@ -326,22 +326,17 @@ static int cpio_mkfile(const char *name, const char *location,
 		buf.st_mtime = 0xffffffff;
 	}
 
-	filebuf = malloc(buf.st_size);
-	if (!filebuf) {
-		fprintf (stderr, "out of memory\n");
-		goto error;
-	}
-
-	retval = read (file, filebuf, buf.st_size);
-	if (retval < 0) {
-		fprintf (stderr, "Can not read %s file\n", location);
+	if (buf.st_size > 0xffffffff) {
+		fprintf(stderr, "%s: Size exceeds maximum cpio file size\n",
+			location);
 		goto error;
 	}
 
 	size = 0;
 	for (i = 1; i <= nlinks; i++) {
 		/* data goes on last link */
-		if (i == nlinks) size = buf.st_size;
+		if (i == nlinks)
+			size = buf.st_size;
 
 		if (name[0] == '/')
 			name++;
@@ -366,23 +361,34 @@ static int cpio_mkfile(const char *name, const char *location,
 		push_string(name);
 		push_pad();
 
-		if (size) {
-			if (fwrite(filebuf, size, 1, stdout) != 1) {
+		while (size) {
+			unsigned char filebuf[65536];
+			ssize_t this_read;
+			size_t this_size = MIN(size, sizeof(filebuf));
+
+			this_read = read(file, filebuf, this_size);
+			if (this_read <= 0 || this_read > this_size) {
+				fprintf(stderr, "Can not read %s file\n", location);
+				goto error;
+			}
+
+			if (fwrite(filebuf, this_read, 1, stdout) != 1) {
 				fprintf(stderr, "writing filebuf failed\n");
 				goto error;
 			}
-			offset += size;
-			push_pad();
+			offset += this_read;
+			size -= this_read;
 		}
+		push_pad();
 
 		name += namesize;
 	}
 	ino++;
 	rc = 0;
-	
+
 error:
-	if (filebuf) free(filebuf);
-	if (file >= 0) close(file);
+	if (file >= 0)
+		close(file);
 	return rc;
 }
 
-- 
2.31.1

[PATCH v5 4/5] gen_init_cpio: support file checksum archiving

[David Disseldorp]

Documentation/driver-api/early-userspace/buffer-format.rst includes the
specification for crc-enabled cpio archives. Implement support for this
format in gen_init_cpio via a new '-c' parameter.

Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 usr/gen_init_cpio.c | 54 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
index 9a0f8c37273a..dc838e26a5b9 100644
--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <string.h>
@@ -25,6 +27,7 @@
 static unsigned int offset;
 static unsigned int ino = 721;
 static time_t default_mtime;
+static bool do_csum = false;
 
 struct file_handler {
 	const char *type;
@@ -78,7 +81,7 @@ static void cpio_trailer(void)
 
 	sprintf(s, "%s%08X%08X%08lX%08lX%08X%08lX"
 	       "%08X%08X%08X%08X%08X%08X%08X",
-		"070701",		/* magic */
+		do_csum ? "070702" : "070701", /* magic */
 		0,			/* ino */
 		0,			/* mode */
 		(long) 0,		/* uid */
@@ -110,7 +113,7 @@ static int cpio_mkslink(const char *name, const char *target,
 		name++;
 	sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
 	       "%08X%08X%08X%08X%08X%08X%08X",
-		"070701",		/* magic */
+		do_csum ? "070702" : "070701", /* magic */
 		ino++,			/* ino */
 		S_IFLNK | mode,		/* mode */
 		(long) uid,		/* uid */
@@ -159,7 +162,7 @@ static int cpio_mkgeneric(const char *name, unsigned int mode,
 		name++;
 	sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
 	       "%08X%08X%08X%08X%08X%08X%08X",
-		"070701",		/* magic */
+		do_csum ? "070702" : "070701", /* magic */
 		ino++,			/* ino */
 		mode,			/* mode */
 		(long) uid,		/* uid */
@@ -253,7 +256,7 @@ static int cpio_mknod(const char *name, unsigned int mode,
 		name++;
 	sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
 	       "%08X%08X%08X%08X%08X%08X%08X",
-		"070701",		/* magic */
+		do_csum ? "070702" : "070701", /* magic */
 		ino++,			/* ino */
 		mode,			/* mode */
 		(long) uid,		/* uid */
@@ -293,6 +296,29 @@ static int cpio_mknod_line(const char *line)
 	return rc;
 }
 
+static int cpio_mkfile_csum(int fd, unsigned long size, uint32_t *csum)
+{
+	while (size) {
+		unsigned char filebuf[65536];
+		ssize_t this_read;
+		size_t i, this_size = MIN(size, sizeof(filebuf));
+
+		this_read = read(fd, filebuf, this_size);
+		if (this_read <= 0 || this_read > this_size)
+			return -1;
+
+		for (i = 0; i < this_read; i++)
+			*csum += filebuf[i];
+
+		size -= this_read;
+	}
+	/* seek back to the start for data segment I/O */
+	if (lseek(fd, 0, SEEK_SET) < 0)
+		return -1;
+
+	return 0;
+}
+
 static int cpio_mkfile(const char *name, const char *location,
 			unsigned int mode, uid_t uid, gid_t gid,
 			unsigned int nlinks)
@@ -305,6 +331,7 @@ static int cpio_mkfile(const char *name, const char *location,
 	int rc = -1;
 	int namesize;
 	unsigned int i;
+	uint32_t csum = 0;
 
 	mode |= S_IFREG;
 
@@ -332,6 +359,11 @@ static int cpio_mkfile(const char *name, const char *location,
 		goto error;
 	}
 
+	if (do_csum && cpio_mkfile_csum(file, buf.st_size, &csum) < 0) {
+		fprintf(stderr, "Failed to checksum file %s\n", location);
+		goto error;
+	}
+
 	size = 0;
 	for (i = 1; i <= nlinks; i++) {
 		/* data goes on last link */
@@ -343,7 +375,7 @@ static int cpio_mkfile(const char *name, const char *location,
 		namesize = strlen(name) + 1;
 		sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
 		       "%08lX%08X%08X%08X%08X%08X%08X",
-			"070701",		/* magic */
+			do_csum ? "070702" : "070701", /* magic */
 			ino,			/* ino */
 			mode,			/* mode */
 			(long) uid,		/* uid */
@@ -356,7 +388,7 @@ static int cpio_mkfile(const char *name, const char *location,
 			0,			/* rmajor */
 			0,			/* rminor */
 			namesize,		/* namesize */
-			0);			/* chksum */
+			size ? csum : 0);	/* chksum */
 		push_hdr(s);
 		push_string(name);
 		push_pad();
@@ -464,7 +496,7 @@ static int cpio_mkfile_line(const char *line)
 static void usage(const char *prog)
 {
 	fprintf(stderr, "Usage:\n"
-		"\t%s [-t <timestamp>] <cpio_list>\n"
+		"\t%s [-t <timestamp>] [-c] <cpio_list>\n"
 		"\n"
 		"<cpio_list> is a file containing newline separated entries that\n"
 		"describe the files to be included in the initramfs archive:\n"
@@ -499,7 +531,8 @@ static void usage(const char *prog)
 		"\n"
 		"<timestamp> is time in seconds since Epoch that will be used\n"
 		"as mtime for symlinks, special files and directories. The default\n"
-		"is to use the current time for these entries.\n",
+		"is to use the current time for these entries.\n"
+		"-c: calculate and store 32-bit checksums for file data.\n",
 		prog);
 }
 
@@ -541,7 +574,7 @@ int main (int argc, char *argv[])
 
 	default_mtime = time(NULL);
 	while (1) {
-		int opt = getopt(argc, argv, "t:h");
+		int opt = getopt(argc, argv, "t:ch");
 		char *invalid;
 
 		if (opt == -1)
@@ -556,6 +589,9 @@ int main (int argc, char *argv[])
 				exit(1);
 			}
 			break;
+		case 'c':
+			do_csum = true;
+			break;
 		case 'h':
 		case '?':
 			usage(argv[0]);
-- 
2.31.1

[PATCH v5 5/5] initramfs: support cpio extraction with file checksums

[David Disseldorp]

Add support for the extraction of crc-enabled "070702" cpio archives, as
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.

Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 init/initramfs.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 5b4ca8ecadb5..ead3e2839f44 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -19,8 +19,11 @@
 
 #include "initramfs_mtime.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;
 
@@ -35,6 +38,13 @@ 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;
@@ -118,8 +128,6 @@ static void __init free_hash(void)
 	}
 }
 
-static __initdata time64_t mtime;
-
 /* cpio header parsing */
 
 static __initdata unsigned long ino, major, minor, nlink;
@@ -128,15 +136,17 @@ static __initdata unsigned long body_len, name_len;
 static __initdata uid_t uid;
 static __initdata gid_t gid;
 static __initdata unsigned rdev;
+static __initdata time64_t mtime;
+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);
 	}
@@ -151,6 +161,7 @@ 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 */
@@ -219,7 +230,11 @@ 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
@@ -314,6 +329,7 @@ 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);
@@ -346,6 +362,8 @@ 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;
-- 
2.31.1

Re: initramfs: "crc" cpio format and INITRAMFS_PRESERVE_MTIME

[David Disseldorp]

On Tue, 14 Dec 2021 00:20:03 +0100, David Disseldorp wrote:

> This patchset does some minor initramfs refactoring and allows cpio
> entry mtime preservation to be disabled via a new Kconfig
> INITRAMFS_PRESERVE_MTIME option.
> Patches 3/5 to 5/5 implement support for creation and extraction of
> "crc" cpio archives, which carry file data checksums. Basic tests for
> this functionality can be found at
> Link: https://github.com/rapido-linux/rapido/pull/163
> 
> Changes since v4, following feedback from Matthew Wilcox:
> - implement cpio "crc" archive creation and extraction
> - add patch to fix gen_init_cpio short read handling
> - drop now-unnecessary "crc" documentation and error msg changes

Ping, any feedback on this round?

Thanks, David

> Changes since v3, following feedback from Martin Wilck:
> - 4/4: keep vfs_utimes() call in do_copy() path
>   + drop [PATCH v3 4/5] initramfs: use do_utime() wrapper consistently
>   + add do_utime_path() helper
>   + clean up timespec64 initialisation
> - 4/4: move all mtime preservation logic to initramfs_mtime.h and drop
>   separate .c
> - 4/4: improve commit message
> 
> 
>  init/Kconfig           | 10 +++++
>  init/initramfs.c       | 89 +++++++++++++++-------------------------
>  init/initramfs_mtime.h | 50 +++++++++++++++++++++++
>  usr/gen_init_cpio.c    | 92 ++++++++++++++++++++++++++++++------------
>  4 files changed, 159 insertions(+), 82 deletions(-)