[v2,3/3] initramfs: introduce do_readxattrs()
diff mbox series

Message ID 20190509112420.15671-4-roberto.sassu@huawei.com
State New
Headers show
Series
  • initramfs: add support for xattrs in the initial ram disk
Related show

Commit Message

Roberto Sassu May 9, 2019, 11:24 a.m. UTC
This patch adds support for an alternative method to add xattrs to files in
the rootfs filesystem. Instead of extracting them directly from the ram
disk image, they are extracted from a regular file called .xattr-list, that
can be added by any ram disk generator available today.

.xattr-list can be generated by executing:

$ getfattr --absolute-names -d -P -R -e hex -m - \
      <file list> | xattr.awk -b > ${initdir}/.xattr-list

where the content of the xattr.awk script is:

#! /usr/bin/awk -f
{
  if (!length($0)) {
    printf("%.10x%s\0", len, file);
    for (x in xattr) {
      printf("%.8x%s\0", xattr_len[x], x);
      for (i = 0; i < length(xattr[x]) / 2; i++) {
        printf("%c", strtonum("0x"substr(xattr[x], i * 2 + 1, 2)));
      }
    }
    i = 0;
    delete xattr;
    delete xattr_len;
    next;
  };
  if (i == 0) {
    file=$3;
    len=length(file) + 8 + 1;
  }
  if (i > 0) {
    split($0, a, "=");
    xattr[a[1]]=substr(a[2], 3);
    xattr_len[a[1]]=length(a[1]) + 1 + 8 + length(xattr[a[1]]) / 2;
    len+=xattr_len[a[1]];
  };
  i++;
}

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 init/initramfs.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

Comments

Jann Horn May 10, 2019, 9:33 p.m. UTC | #1
On Thu, May 09, 2019 at 01:24:20PM +0200, Roberto Sassu wrote:
> This patch adds support for an alternative method to add xattrs to files in
> the rootfs filesystem. Instead of extracting them directly from the ram
> disk image, they are extracted from a regular file called .xattr-list, that
> can be added by any ram disk generator available today.
[...]
> +struct path_hdr {
> +	char p_size[10]; /* total size including p_size field */
> +	char p_data[];  /* <path>\0<xattrs> */
> +};
> +
> +static int __init do_readxattrs(void)
> +{
> +	struct path_hdr hdr;
> +	char str[sizeof(hdr.p_size) + 1];
> +	unsigned long file_entry_size;
> +	size_t size, name_buf_size, total_size;
> +	struct kstat st;
> +	int ret, fd;
> +
> +	ret = vfs_lstat(XATTR_LIST_FILENAME, &st);
> +	if (ret < 0)
> +		return ret;
> +
> +	total_size = st.size;
> +
> +	fd = ksys_open(XATTR_LIST_FILENAME, O_RDONLY, 0);
> +	if (fd < 0)
> +		return fd;
> +
> +	while (total_size) {
> +		size = ksys_read(fd, (char *)&hdr, sizeof(hdr));
[...]
> +	ksys_close(fd);
> +
> +	if (ret < 0)
> +		error("Unable to parse xattrs");
> +
> +	return ret;
> +}

Please use something like filp_open()+kernel_read()+fput() instead of
ksys_open()+ksys_read()+ksys_close(). I understand that some of the init
code needs to use the syscall wrappers because no equivalent VFS
functions are available, but please use the VFS functions when that's
easy to do.
Roberto Sassu May 13, 2019, 1:03 p.m. UTC | #2
On 5/10/2019 11:33 PM, Jann Horn wrote:
> On Thu, May 09, 2019 at 01:24:20PM +0200, Roberto Sassu wrote:
>> This patch adds support for an alternative method to add xattrs to files in
>> the rootfs filesystem. Instead of extracting them directly from the ram
>> disk image, they are extracted from a regular file called .xattr-list, that
>> can be added by any ram disk generator available today.
> [...]
>> +struct path_hdr {
>> +	char p_size[10]; /* total size including p_size field */
>> +	char p_data[];  /* <path>\0<xattrs> */
>> +};
>> +
>> +static int __init do_readxattrs(void)
>> +{
>> +	struct path_hdr hdr;
>> +	char str[sizeof(hdr.p_size) + 1];
>> +	unsigned long file_entry_size;
>> +	size_t size, name_buf_size, total_size;
>> +	struct kstat st;
>> +	int ret, fd;
>> +
>> +	ret = vfs_lstat(XATTR_LIST_FILENAME, &st);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	total_size = st.size;
>> +
>> +	fd = ksys_open(XATTR_LIST_FILENAME, O_RDONLY, 0);
>> +	if (fd < 0)
>> +		return fd;
>> +
>> +	while (total_size) {
>> +		size = ksys_read(fd, (char *)&hdr, sizeof(hdr));
> [...]
>> +	ksys_close(fd);
>> +
>> +	if (ret < 0)
>> +		error("Unable to parse xattrs");
>> +
>> +	return ret;
>> +}
> 
> Please use something like filp_open()+kernel_read()+fput() instead of
> ksys_open()+ksys_read()+ksys_close(). I understand that some of the init
> code needs to use the syscall wrappers because no equivalent VFS
> functions are available, but please use the VFS functions when that's
> easy to do.

Ok. Thanks for the suggestion.

Roberto

Patch
diff mbox series

diff --git a/init/initramfs.c b/init/initramfs.c
index 98c2aa4b5ab4..91f35a84c592 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -11,6 +11,9 @@ 
 #include <linux/utime.h>
 #include <linux/file.h>
 
+#define XATTR_LIST_FILENAME ".xattr-list"
+
+
 static ssize_t __init xwrite(int fd, const char *p, size_t count)
 {
 	ssize_t out = 0;
@@ -451,6 +454,91 @@  static int __init do_setxattrs(void)
 	return 0;
 }
 
+struct path_hdr {
+	char p_size[10]; /* total size including p_size field */
+	char p_data[];  /* <path>\0<xattrs> */
+};
+
+static int __init do_readxattrs(void)
+{
+	struct path_hdr hdr;
+	char str[sizeof(hdr.p_size) + 1];
+	unsigned long file_entry_size;
+	size_t size, name_buf_size, total_size;
+	struct kstat st;
+	int ret, fd;
+
+	ret = vfs_lstat(XATTR_LIST_FILENAME, &st);
+	if (ret < 0)
+		return ret;
+
+	total_size = st.size;
+
+	fd = ksys_open(XATTR_LIST_FILENAME, O_RDONLY, 0);
+	if (fd < 0)
+		return fd;
+
+	while (total_size) {
+		size = ksys_read(fd, (char *)&hdr, sizeof(hdr));
+		if (size != sizeof(hdr)) {
+			ret = -EIO;
+			goto out;
+		}
+
+		total_size -= size;
+
+		memcpy(str, hdr.p_size, sizeof(hdr.p_size));
+		ret = kstrtoul(str, 16, &file_entry_size);
+		if (ret < 0)
+			goto out;
+
+		file_entry_size -= sizeof(sizeof(hdr.p_size));
+		if (file_entry_size > total_size) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		name_buf = vmalloc(file_entry_size);
+		if (!name_buf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		size = ksys_read(fd, name_buf, file_entry_size);
+		if (size != file_entry_size) {
+			ret = -EIO;
+			goto out_free;
+		}
+
+		total_size -= size;
+
+		name_buf_size = strnlen(name_buf, file_entry_size);
+		if (name_buf_size == file_entry_size) {
+			ret = -EINVAL;
+			goto out_free;
+		}
+
+		xattr_buf = name_buf + name_buf_size + 1;
+		xattr_len = file_entry_size - name_buf_size - 1;
+
+		ret = do_setxattrs();
+		vfree(name_buf);
+		name_buf = NULL;
+
+		if (ret < 0)
+			break;
+	}
+out_free:
+	vfree(name_buf);
+out:
+	ksys_close(fd);
+
+	if (ret < 0)
+		error("Unable to parse xattrs");
+
+	return ret;
+}
+
 static __initdata int (*actions[])(void) = {
 	[Start]		= do_start,
 	[Collect]	= do_collect,
@@ -554,6 +642,7 @@  static char * __init unpack_to_rootfs(char *buf, unsigned long len)
 		buf += my_inptr;
 		len -= my_inptr;
 	}
+	do_readxattrs();
 	dir_utime();
 	kfree(name_buf);
 	kfree(symlink_buf);