Release 4.10 fs/xattr.c

/*
  File: fs/xattr.c

  Extended attribute handling.

  Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
  Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 */
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/evm.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/fsnotify.h>
#include <linux/audit.h>
#include <linux/vmalloc.h>
#include <linux/posix_acl_xattr.h>

#include <linux/uaccess.h>


static const char *

strcmp_prefix(const char *a, const char *a_prefix)
{
	while (*a_prefix && *a == *a_prefix) {
		a++;
		a_prefix++;
	}
	return *a_prefix ? NULL : a;
}

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/*
 * In order to implement different sets of xattr operations for each xattr
 * prefix, a filesystem should create a null-terminated array of struct
 * xattr_handler (one for each prefix) and hang a pointer to it off of the
 * s_xattr field of the superblock.
 */

#define for_each_xattr_handler(handlers, handler)		\
	if (handlers)                                           \
                for ((handler) = *(handlers)++;                 \
                        (handler) != NULL;                      \
                        (handler) = *(handlers)++)

/*
 * Find the xattr_handler with the matching prefix.
 */

static const struct xattr_handler *

xattr_resolve_name(struct inode *inode, const char **name)
{
	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
	const struct xattr_handler *handler;

	if (!(inode->i_opflags & IOP_XATTR)) {
		if (unlikely(is_bad_inode(inode)))
			return ERR_PTR(-EIO);
		return ERR_PTR(-EOPNOTSUPP);
	}
	for_each_xattr_handler(handlers, handler) {
		const char *n;

		n = strcmp_prefix(*name, xattr_prefix(handler));
		if (n) {
			if (!handler->prefix ^ !*n) {
				if (*n)
					continue;
				return ERR_PTR(-EINVAL);
			}
			*name = n;
			return handler;
		}
	}
	return ERR_PTR(-EOPNOTSUPP);
}

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andreas gruenbacher
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/*
 * Check permissions for extended attribute access.  This is a bit complicated
 * because different namespaces have very different rules.
 */

static int

xattr_permission(struct inode *inode, const char *name, int mask)
{
	/*
         * We can never set or remove an extended attribute on a read-only
         * filesystem  or on an immutable / append-only inode.
         */
	if (mask & MAY_WRITE) {
		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
			return -EPERM;
		/*
                 * Updating an xattr will likely cause i_uid and i_gid
                 * to be writen back improperly if their true value is
                 * unknown to the vfs.
                 */
		if (HAS_UNMAPPED_ID(inode))
			return -EPERM;
	}

	/*
         * No restriction for security.* and system.* from the VFS.  Decision
         * on these is left to the underlying filesystem / security module.
         */
	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
		return 0;

	/*
         * The trusted.* namespace can only be accessed by privileged users.
         */
	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
		if (!capable(CAP_SYS_ADMIN))
			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
		return 0;
	}

	/*
         * In the user.* namespace, only regular files and directories can have
         * extended attributes. For sticky directories, only the owner and
         * privileged users can write attributes.
         */
	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
		    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
			return -EPERM;
	}

	return inode_permission(inode, mask);
}

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andrew morton
andrew morton
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andreas gruenbacher
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25.96%
2
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eric w. biederman
eric w. biederman
12
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1
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serge hallyn
serge hallyn
1
0.48%
1
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al viro
al viro
1
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satyam sharma
satyam sharma
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int

__vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
	       const void *value, size_t size, int flags)
{
	const struct xattr_handler *handler;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->set)
		return -EOPNOTSUPP;
	if (size == 0)
		value = "";  /* empty EA, do not remove */
	return handler->set(handler, dentry, inode, name, value, size, flags);
}
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andreas gruenbacher
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EXPORT_SYMBOL(__vfs_setxattr);

/**
 *  __vfs_setxattr_noperm - perform setxattr operation without performing
 *  permission checks.
 *
 *  @dentry - object to perform setxattr on
 *  @name - xattr name to set
 *  @value - value to set @name to
 *  @size - size of @value
 *  @flags - flags to pass into filesystem operations
 *
 *  returns the result of the internal setxattr or setsecurity operations.
 *
 *  This function requires the caller to lock the inode's i_mutex before it
 *  is executed. It also assumes that the caller will make the appropriate
 *  permission checks.
 */


int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
		const void *value, size_t size, int flags)
{
	struct inode *inode = dentry->d_inode;
	int error = -EAGAIN;
	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
				   XATTR_SECURITY_PREFIX_LEN);

	if (issec)
		inode->i_flags &= ~S_NOSEC;
	if (inode->i_opflags & IOP_XATTR) {
		error = __vfs_setxattr(dentry, inode, name, value, size, flags);
		if (!error) {
			fsnotify_xattr(dentry);
			security_inode_post_setxattr(dentry, name, value,
						     size, flags);
		}
	} else {
		if (unlikely(is_bad_inode(inode)))
			return -EIO;
	}
	if (error == -EAGAIN) {
		error = -EOPNOTSUPP;

		if (issec) {
			const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;

			error = security_inode_setsecurity(inode, suffix, value,
							   size, flags);
			if (!error)
				fsnotify_xattr(dentry);
		}
	}

	return error;
}


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christoph hellwig
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andreas gruenbacher
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andi kleen
andi kleen
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david p. quigley
david p. quigley
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david howells
david howells
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al viro
al viro
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int

vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
		size_t size, int flags)
{
	struct inode *inode = dentry->d_inode;
	int error;

	error = xattr_permission(inode, name, MAY_WRITE);
	if (error)
		return error;

	inode_lock(inode);
	error = security_inode_setxattr(dentry, name, value, size, flags);
	if (error)
		goto out;

	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);

out:
	inode_unlock(inode);
	return error;
}
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david p. quigley
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christoph hellwig
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EXPORT_SYMBOL_GPL(vfs_setxattr);


ssize_t

xattr_getsecurity(struct inode *inode, const char *name, void *value,
			size_t size)
{
	void *buffer = NULL;
	ssize_t len;

	if (!value || !size) {
		len = security_inode_getsecurity(inode, name, &buffer, false);
		goto out_noalloc;
	}

	len = security_inode_getsecurity(inode, name, &buffer, true);
	if (len < 0)
		return len;
	if (size < len) {
		len = -ERANGE;
		goto out;
	}
	memcpy(value, buffer, len);
out:
	security_release_secctx(buffer, len);
out_noalloc:
	return len;
}
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david p. quigley
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christoph hellwig
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EXPORT_SYMBOL_GPL(xattr_getsecurity);

/*
 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 *
 * Allocate memory, if not already allocated, or re-allocate correct size,
 * before retrieving the extended attribute.
 *
 * Returns the result of alloc, if failed, or the getxattr operation.
 */

ssize_t

vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
		   size_t xattr_size, gfp_t flags)
{
	const struct xattr_handler *handler;
	struct inode *inode = dentry->d_inode;
	char *value = *xattr_value;
	int error;

	error = xattr_permission(inode, name, MAY_READ);
	if (error)
		return error;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->get)
		return -EOPNOTSUPP;
	error = handler->get(handler, dentry, inode, name, NULL, 0);
	if (error < 0)
		return error;

	if (!value || (error > xattr_size)) {
		value = krealloc(*xattr_value, error + 1, flags);
		if (!value)
			return -ENOMEM;
		memset(value, 0, error + 1);
	}

	error = handler->get(handler, dentry, inode, name, value, error);
	*xattr_value = value;
	return error;
}

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ssize_t

__vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
	       void *value, size_t size)
{
	const struct xattr_handler *handler;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->get)
		return -EOPNOTSUPP;
	return handler->get(handler, dentry, inode, name, value, size);
}
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andreas gruenbacher
andreas gruenbacher
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david p. quigley
david p. quigley
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EXPORT_SYMBOL(__vfs_getxattr);


ssize_t

vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
{
	struct inode *inode = dentry->d_inode;
	int error;

	error = xattr_permission(inode, name, MAY_READ);
	if (error)
		return error;

	error = security_inode_getxattr(dentry, name);
	if (error)
		return error;

	if (!strncmp(name, XATTR_SECURITY_PREFIX,
				XATTR_SECURITY_PREFIX_LEN)) {
		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
		int ret = xattr_getsecurity(inode, suffix, value, size);
		/*
                 * Only overwrite the return value if a security module
                 * is actually active.
                 */
		if (ret == -EOPNOTSUPP)
			goto nolsm;
		return ret;
	}
nolsm:
	return __vfs_getxattr(dentry, inode, name, value, size);
}
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christoph hellwig
christoph hellwig
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david p. quigley
david p. quigley
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andrew morton
andrew morton
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andreas gruenbacher
andreas gruenbacher
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1
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al viro
al viro
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1
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david howells
david howells
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EXPORT_SYMBOL_GPL(vfs_getxattr);


ssize_t

vfs_listxattr(struct dentry *dentry, char *list, size_t size)
{
	struct inode *inode = d_inode(dentry);
	ssize_t error;

	error = security_inode_listxattr(dentry);
	if (error)
		return error;
	if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
		error = -EOPNOTSUPP;
		error = inode->i_op->listxattr(dentry, list, size);
	} else {
		error = security_inode_listsecurity(inode, list, size);
		if (size && error > size)
			error = -ERANGE;
	}
	return error;
}
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bill nottingham
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andreas gruenbacher
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EXPORT_SYMBOL_GPL(vfs_listxattr);


int

__vfs_removexattr(struct dentry *dentry, const char *name)
{
	struct inode *inode = d_inode(dentry);
	const struct xattr_handler *handler;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->set)
		return -EOPNOTSUPP;
	return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
}
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andreas gruenbacher
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christoph hellwig
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1
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david howells
david howells
1
1.18%
1
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85
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100.00%


EXPORT_SYMBOL(__vfs_removexattr);


int

vfs_removexattr(struct dentry *dentry, const char *name)
{
	struct inode *inode = dentry->d_inode;
	int error;

	error = xattr_permission(inode, name, MAY_WRITE);
	if (error)
		return error;

	inode_lock(inode);
	error = security_inode_removexattr(dentry, name);
	if (error)
		goto out;

	error = __vfs_removexattr(dentry, name);

	if (!error) {
		fsnotify_xattr(dentry);
		evm_inode_post_removexattr(dentry, name);
	}

out:
	inode_unlock(inode);
	return error;
}
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christoph hellwig
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andreas gruenbacher
27
25.96%
1
14.29%
andrew morton
andrew morton
18
17.31%
1
14.29%
mimi zohar
mimi zohar
13
12.50%
2
28.57%
dmitry kasatkin
dmitry kasatkin
9
8.65%
1
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al viro
al viro
2
1.92%
1
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104
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7
100.00%


EXPORT_SYMBOL_GPL(vfs_removexattr);


/*
 * Extended attribute SET operations
 */

static long

setxattr(struct dentry *d, const char __user *name, const void __user *value,
	 size_t size, int flags)
{
	int error;
	void *kvalue = NULL;
	char kname[XATTR_NAME_MAX + 1];

	if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
		return -EINVAL;

	error = strncpy_from_user(kname, name, sizeof(kname));
	if (error == 0 || error == sizeof(kname))
		error = -ERANGE;
	if (error < 0)
		return error;

	if (size) {
		if (size > XATTR_SIZE_MAX)
			return -E2BIG;
		kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
		if (!kvalue) {
			kvalue = vmalloc(size);
			if (!kvalue)
				return -ENOMEM;
		}
		if (copy_from_user(kvalue, value, size)) {
			error = -EFAULT;
			goto out;
		}
		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
			posix_acl_fix_xattr_from_user(kvalue, size);
	}

	error = vfs_setxattr(d, kname, kvalue, size, flags);
out:
	kvfree(kvalue);

	return error;
}

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linus torvalds
78
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1
9.09%
andrew morton
andrew morton
57
24.89%
2
18.18%
nathan scott
nathan scott
32
13.97%
1
9.09%
eric w. biederman
eric w. biederman
31
13.54%
1
9.09%
stephen d. smalley
stephen d. smalley
15
6.55%
1
9.09%
christoph hellwig
christoph hellwig
7
3.06%
1
9.09%
richard weinberger
richard weinberger
3
1.31%
1
9.09%
li zefan
li zefan
2
0.87%
1
9.09%
andries brouwer
andries brouwer
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0.87%
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david howells
david howells
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static int path_setxattr(const char __user *pathname,
			 const char __user *name, const void __user *value,
			 size_t size, int flags, unsigned int lookup_flags)
{
	struct path path;
	int error;
retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (error)
		return error;
	error = mnt_want_write(path.mnt);
	if (!error) {
		error = setxattr(path.dentry, name, value, size, flags);
		mnt_drop_write(path.mnt);
	}
	path_put(&path);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}

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linus torvalds
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eric biggers
eric biggers
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jeff layton
jeff layton
25
19.08%
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dave hansen
dave hansen
23
17.56%
1
14.29%
al viro
al viro
4
3.05%
1
14.29%
jan blunck
jan blunck
4
3.05%
2
28.57%
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131
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SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
		const char __user *, name, const void __user *, value,
		size_t, size, int, flags)
{
	return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
}


SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
		const char __user *, name, const void __user *, value,
		size_t, size, int, flags)
{
	return path_setxattr(pathname, name, value, size, flags, 0);
}


SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
		const void __user *,value, size_t, size, int, flags)
{
	struct fd f = fdget(fd);
	int error = -EBADF;

	if (!f.file)
		return error;
	audit_file(f.file);
	error = mnt_want_write_file(f.file);
	if (!error) {
		error = setxattr(f.file->f_path.dentry, name, value, size, flags);
		mnt_drop_write_file(f.file);
	}
	fdput(f);
	return error;
}

/*
 * Extended attribute GET operations
 */

static ssize_t

getxattr(struct dentry *d, const char __user *name, void __user *value,
	 size_t size)
{
	ssize_t error;
	void *kvalue = NULL;
	char kname[XATTR_NAME_MAX + 1];

	error = strncpy_from_user(kname, name, sizeof(kname));
	if (error == 0 || error == sizeof(kname))
		error = -ERANGE;
	if (error < 0)
		return error;

	if (size) {
		if (size > XATTR_SIZE_MAX)
			size = XATTR_SIZE_MAX;
		kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
		if (!kvalue) {
			kvalue = vmalloc(size);
			if (!kvalue)
				return -ENOMEM;
		}
	}

	error = vfs_getxattr(d, kname, kvalue, size);
	if (error > 0) {
		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
			posix_acl_fix_xattr_to_user(kvalue, size);
		if (size && copy_to_user(value, kvalue, error))
			error = -EFAULT;
	} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
		/* The file system tried to returned a value bigger
                   than XATTR_SIZE_MAX bytes. Not possible. */
		error = -E2BIG;
	}

	kvfree(kvalue);

	return error;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
linus torvalds
linus torvalds
85
36.80%
1
6.25%
andrew morton
andrew morton
45
19.48%
2
12.50%
nathan scott
nathan scott
35
15.15%
3
18.75%
eric w. biederman
eric w. biederman
31
13.42%
1
6.25%
sasha levin
sasha levin
14
6.06%
1
6.25%
stephen d. smalley
stephen d. smalley
10
4.33%
2
12.50%
greg kroah-hartman
greg kroah-hartman
3
1.30%
1
6.25%
richard weinberger
richard weinberger
3
1.30%
1
6.25%
andries brouwer
andries brouwer
2
0.87%
1
6.25%
david howells
david howells
1
0.43%
1
6.25%
james morris
james morris
1
0.43%
1
6.25%
christoph hellwig
christoph hellwig
1
0.43%
1
6.25%
Total
231
100.00%
16
100.00%



static ssize_t path_getxattr(const char __user *pathname,
			     const char __user *name, void __user *value,
			     size_t size, unsigned int lookup_flags)
{
	struct path path;
	ssize_t error;
retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (error)
		return error;
	error = getxattr(path.dentry, name, value, size);
	path_put(&path);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
linus torvalds
linus torvalds
40
39.22%
1
14.29%
eric biggers
eric biggers
28
27.45%
1
14.29%
jeff layton
jeff layton
25
24.51%
1
14.29%
al viro
al viro
4
3.92%
1
14.29%
jan blunck
jan blunck
4
3.92%
2
28.57%
nathan scott
nathan scott
1
0.98%
1
14.29%
Total
102
100.00%
7
100.00%


SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
		const char __user *, name, void __user *, value, size_t, size)
{
	return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
}


SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
		const char __user *, name, void __user *, value, size_t, size)
{
	return path_getxattr(pathname, name, value, size, 0);
}


SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
		void __user *, value, size_t, size)
{
	struct fd f = fdget(fd);
	ssize_t error = -EBADF;

	if (!f.file)
		return error;
	audit_file(f.file);
	error = getxattr(f.file->f_path.dentry, name, value, size);
	fdput(f);
	return error;
}

/*
 * Extended attribute LIST operations
 */

static ssize_t

listxattr(struct dentry *d, char __user *list, size_t size)
{
	ssize_t error;
	char *klist = NULL;

	if (size) {
		if (size > XATTR_LIST_MAX)
			size = XATTR_LIST_MAX;
		klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
		if (!klist) {
			klist = vmalloc(