[PATCH v3 1/2] initramfs: set extended attributes

From: Roberto Sassu
Date: Fri May 17 2019 - 13:01:46 EST


From: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>

This patch adds xattrs to a file, with name and value taken from a supplied
buffer. The data format is:

<xattr #N data len (ASCII, 8 chars)><xattr #N name>\0<xattr #N value>

[kamensky: fixed restoring of xattrs for symbolic links by using
sys_lsetxattr() instead of sys_setxattr()]

[sassu: removed state management, kept only do_setxattrs(), replaced
sys_lsetxattr() with vfs_setxattr(), added check for
xattr_entry_size, added check for hdr->c_size, replaced strlen()
with strnlen(); moved do_setxattrs() before do_name()]

Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Victor Kamensky <kamensky@xxxxxxxxx>
Signed-off-by: Taras Kondratiuk <takondra@xxxxxxxxx>
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
init/initramfs.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 69 insertions(+), 2 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 435a428c2af1..0c6dd1d5d3f6 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -10,6 +10,8 @@
#include <linux/syscalls.h>
#include <linux/utime.h>
#include <linux/file.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>

static ssize_t __init xwrite(int fd, const char *p, size_t count)
{
@@ -146,7 +148,8 @@ static __initdata time64_t mtime;

static __initdata unsigned long ino, major, minor, nlink;
static __initdata umode_t mode;
-static __initdata unsigned long body_len, name_len;
+static __initdata u32 name_len, xattr_len;
+static __initdata u64 body_len;
static __initdata uid_t uid;
static __initdata gid_t gid;
static __initdata unsigned rdev;
@@ -218,7 +221,7 @@ static void __init read_into(char *buf, unsigned size, enum state next)
}
}

-static __initdata char *header_buf, *symlink_buf, *name_buf;
+static __initdata char *header_buf, *symlink_buf, *name_buf, *xattr_buf;

static int __init do_start(void)
{
@@ -315,6 +318,70 @@ static int __init maybe_link(void)
return 0;
}

+struct xattr_hdr {
+ char c_size[8]; /* total size including c_size field */
+ char c_data[]; /* <name>\0<value> */
+};
+
+static int __init __maybe_unused do_setxattrs(char *pathname)
+{
+ char *buf = xattr_buf;
+ char *bufend = buf + xattr_len;
+ struct xattr_hdr *hdr;
+ char str[sizeof(hdr->c_size) + 1];
+ struct path path;
+
+ if (!xattr_len)
+ return 0;
+
+ str[sizeof(hdr->c_size)] = 0;
+
+ while (buf < bufend) {
+ char *xattr_name, *xattr_value;
+ unsigned long xattr_entry_size;
+ unsigned long xattr_name_size, xattr_value_size;
+ int ret;
+
+ if (buf + sizeof(hdr->c_size) > bufend) {
+ error("malformed xattrs");
+ break;
+ }
+
+ hdr = (struct xattr_hdr *)buf;
+ memcpy(str, hdr->c_size, sizeof(hdr->c_size));
+ ret = kstrtoul(str, 16, &xattr_entry_size);
+ buf += xattr_entry_size;
+ if (ret || buf > bufend || !xattr_entry_size) {
+ error("malformed xattrs");
+ break;
+ }
+
+ xattr_name = hdr->c_data;
+ xattr_name_size = strnlen(xattr_name,
+ xattr_entry_size - sizeof(hdr->c_size));
+ if (xattr_name_size == xattr_entry_size - sizeof(hdr->c_size)) {
+ error("malformed xattrs");
+ break;
+ }
+
+ xattr_value = xattr_name + xattr_name_size + 1;
+ xattr_value_size = buf - xattr_value;
+
+ ret = kern_path(pathname, 0, &path);
+ if (!ret) {
+ ret = vfs_setxattr(path.dentry, xattr_name, xattr_value,
+ xattr_value_size, 0);
+
+ path_put(&path);
+ }
+
+ pr_debug("%s: %s size: %lu val: %s (ret: %d)\n", pathname,
+ xattr_name, xattr_value_size, xattr_value, ret);
+ }
+
+ return 0;
+}
+
static __initdata int wfd;

static int __init do_name(void)
--
2.17.1