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Date: Fri, 24 Feb 2012 19:13:59 +1100 (EST)
From: James Morris <jmorris@...ei.org>
To: Jarkko Sakkinen <jarkko.sakkinen@...el.com>
cc: Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH] tmpfs: security xattr setting on inode creation
On Thu, 23 Feb 2012, Jarkko Sakkinen wrote:
> Adds to generic xattr support introduced in Linux 3.0 by
> implementing initxattrs callback. This enables consulting
> of security attributes from LSM and EVM when inode is
> created.
>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...el.com>
Reviewed-by: James Morris <james.l.morris@...cle.com>
> mm/shmem.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
> 1 files changed, 66 insertions(+), 16 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 7a45ad0..cd367b1 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1478,6 +1478,64 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
> }
>
> /*
> + * Allocate new xattr.
> + */
> +static int shmem_xattr_alloc(size_t size, struct shmem_xattr **new_xattr)
> +{
> + /* wrap around? */
> + size_t len = sizeof(**new_xattr) + size;
> + if (len <= sizeof(**new_xattr))
> + return -ENOMEM;
> +
> + *new_xattr = kmalloc(len, GFP_KERNEL);
> + if (*new_xattr == NULL)
> + return -ENOMEM;
> +
> + (*new_xattr)->size = size;
> + return 0;
> +}
> +
> +/*
> + * Callback for security_inode_init_security() for acquiring xattrs.
> + */
> +static int shmem_initxattrs(struct inode *inode,
> + const struct xattr *xattr_array,
> + void *fs_info)
> +{
> + const struct xattr *xattr;
> + struct shmem_inode_info *info = SHMEM_I(inode);
> + struct shmem_xattr *new_xattr = NULL;
> + size_t len;
> + int err = 0;
> +
> + for (xattr = xattr_array; xattr->name != NULL; xattr++) {
> + err = shmem_xattr_alloc(xattr->value_len, &new_xattr);
> + if (err < 0)
> + return err;
> +
> + len = strlen(xattr->name) + 1;
> + new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
> + GFP_KERNEL);
> + if (new_xattr->name == NULL) {
> + kfree(new_xattr);
> + return -ENOMEM;
> + }
> +
> + memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
> + XATTR_SECURITY_PREFIX_LEN);
> + memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
> + xattr->name, len);
> + memcpy(new_xattr->value, xattr->value, xattr->value_len);
> +
> + spin_lock(&info->lock);
> + list_add(&new_xattr->list, &info->xattr_list);
> + spin_unlock(&info->lock);
> + }
> +
> + return 0;
> +}
> +
> +/*
> * File creation. Allocate an inode, and we're done..
> */
> static int
> @@ -1490,7 +1548,7 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
> if (inode) {
> error = security_inode_init_security(inode, dir,
> &dentry->d_name,
> - NULL, NULL);
> + &shmem_initxattrs, NULL);
> if (error) {
> if (error != -EOPNOTSUPP) {
> iput(inode);
> @@ -1630,7 +1688,7 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
> return -ENOSPC;
>
> error = security_inode_init_security(inode, dir, &dentry->d_name,
> - NULL, NULL);
> + &shmem_initxattrs, NULL);
> if (error) {
> if (error != -EOPNOTSUPP) {
> iput(inode);
> @@ -1731,26 +1789,19 @@ static int shmem_xattr_get(struct dentry *dentry, const char *name,
> return ret;
> }
>
> -static int shmem_xattr_set(struct dentry *dentry, const char *name,
> +static int shmem_xattr_set(struct inode *inode, const char *name,
> const void *value, size_t size, int flags)
> {
> - struct inode *inode = dentry->d_inode;
> struct shmem_inode_info *info = SHMEM_I(inode);
> struct shmem_xattr *xattr;
> struct shmem_xattr *new_xattr = NULL;
> - size_t len;
> int err = 0;
>
> /* value == NULL means remove */
> if (value) {
> - /* wrap around? */
> - len = sizeof(*new_xattr) + size;
> - if (len <= sizeof(*new_xattr))
> - return -ENOMEM;
> -
> - new_xattr = kmalloc(len, GFP_KERNEL);
> - if (!new_xattr)
> - return -ENOMEM;
> + err = shmem_xattr_alloc(size, &new_xattr);
> + if (err < 0)
> + return err;
>
> new_xattr->name = kstrdup(name, GFP_KERNEL);
> if (!new_xattr->name) {
> @@ -1758,7 +1809,6 @@ static int shmem_xattr_set(struct dentry *dentry, const char *name,
> return -ENOMEM;
> }
>
> - new_xattr->size = size;
> memcpy(new_xattr->value, value, size);
> }
>
> @@ -1858,7 +1908,7 @@ static int shmem_setxattr(struct dentry *dentry, const char *name,
> if (size == 0)
> value = ""; /* empty EA, do not remove */
>
> - return shmem_xattr_set(dentry, name, value, size, flags);
> + return shmem_xattr_set(dentry->d_inode, name, value, size, flags);
>
> }
>
> @@ -1878,7 +1928,7 @@ static int shmem_removexattr(struct dentry *dentry, const char *name)
> if (err)
> return err;
>
> - return shmem_xattr_set(dentry, name, NULL, 0, XATTR_REPLACE);
> + return shmem_xattr_set(dentry->d_inode, name, NULL, 0, XATTR_REPLACE);
> }
>
> static bool xattr_is_trusted(const char *name)
> --
> 1.7.5.4
>
> --
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>
--
James Morris
<jmorris@...ei.org>
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