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Message-ID: <CAEjxPJ4fE2z27v+U28smRDKojKbF95dMKnQtustGjiyOrOJ0gA@mail.gmail.com>
Date: Mon, 28 Apr 2025 12:12:21 -0400
From: Stephen Smalley <stephen.smalley.work@...il.com>
To: paul@...l-moore.com
Cc: Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Eric Dumazet <edumazet@...gle.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>, Paolo Abeni <pabeni@...hat.com>,
Willem de Bruijn <willemb@...gle.com>, "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
Ondrej Mosnacek <omosnace@...hat.com>, Casey Schaufler <casey@...aufler-ca.com>, linux-nfs@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
selinux@...r.kernel.org
Subject: Re: [PATCH] security,fs,nfs,net: update security_inode_listsecurity() interface
On Mon, Apr 28, 2025 at 12:00 PM Stephen Smalley
<stephen.smalley.work@...il.com> wrote:
>
> Update the security_inode_listsecurity() interface to allow
> use of the xattr_list_one() helper and update the hook
> implementations.
>
> Link: https://lore.kernel.org/selinux/20250424152822.2719-1-stephen.smalley.work@gmail.com/
>
> Signed-off-by: Stephen Smalley <stephen.smalley.work@...il.com>
> ---
> This patch is relative to the one linked above, which in theory is on
> vfs.fixes but doesn't appear to have been pushed when I looked.
>
> fs/nfs/nfs4proc.c | 9 +++++----
> fs/xattr.c | 20 ++++++++------------
> include/linux/lsm_hook_defs.h | 4 ++--
> include/linux/security.h | 5 +++--
> net/socket.c | 8 +-------
> security/security.c | 16 ++++++++--------
> security/selinux/hooks.c | 10 +++-------
> security/smack/smack_lsm.c | 13 ++++---------
> 8 files changed, 34 insertions(+), 51 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 970f28dbf253..a1d7cb0acb5e 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -8023,12 +8023,13 @@ static int nfs4_xattr_get_nfs4_label(const struct xattr_handler *handler,
> static ssize_t
> nfs4_listxattr_nfs4_label(struct inode *inode, char *list, size_t list_len)
> {
> - int len = 0;
> + ssize_t len = 0;
> + int err;
>
> if (nfs_server_capable(inode, NFS_CAP_SECURITY_LABEL)) {
> - len = security_inode_listsecurity(inode, list, list_len);
> - if (len >= 0 && list_len && len > list_len)
> - return -ERANGE;
> + err = security_inode_listsecurity(inode, &list, &len);
> + if (err)
> + len = err;
That's obviously wrong, sorry for the noise. v2 coming.
> }
> return len;
> }
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 2fc314b27120..fdd2f387bfd5 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -492,9 +492,12 @@ vfs_listxattr(struct dentry *dentry, char *list, size_t size)
> if (inode->i_op->listxattr) {
> error = inode->i_op->listxattr(dentry, list, size);
> } else {
> - error = security_inode_listsecurity(inode, list, size);
> - if (size && error > size)
> - error = -ERANGE;
> + char *buffer = list;
> + ssize_t len = 0;
> +
> + error = security_inode_listsecurity(inode, &buffer, &len);
Also wrong.
> + if (!error)
> + error = len;
> }
> return error;
> }
> @@ -1469,17 +1472,10 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
> if (err)
> return err;
>
> - err = security_inode_listsecurity(inode, buffer, remaining_size);
> - if (err < 0)
> + err = security_inode_listsecurity(inode, &buffer, &remaining_size);
> + if (err)
> return err;
>
> - if (buffer) {
> - if (remaining_size < err)
> - return -ERANGE;
> - buffer += err;
> - }
> - remaining_size -= err;
> -
> read_lock(&xattrs->lock);
> for (rbp = rb_first(&xattrs->rb_root); rbp; rbp = rb_next(rbp)) {
> xattr = rb_entry(rbp, struct simple_xattr, rb_node);
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index bf3bbac4e02a..3c3919dcdebc 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -174,8 +174,8 @@ LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct mnt_idmap *idmap,
> struct inode *inode, const char *name, void **buffer, bool alloc)
> LSM_HOOK(int, -EOPNOTSUPP, inode_setsecurity, struct inode *inode,
> const char *name, const void *value, size_t size, int flags)
> -LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
> - size_t buffer_size)
> +LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char **buffer,
> + ssize_t *remaining_size)
> LSM_HOOK(void, LSM_RET_VOID, inode_getlsmprop, struct inode *inode,
> struct lsm_prop *prop)
> LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index cc9b54d95d22..0efc6a0ab56d 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -457,7 +457,7 @@ int security_inode_getsecurity(struct mnt_idmap *idmap,
> struct inode *inode, const char *name,
> void **buffer, bool alloc);
> int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags);
> -int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
> +int security_inode_listsecurity(struct inode *inode, char **buffer, ssize_t *remaining_size);
> void security_inode_getlsmprop(struct inode *inode, struct lsm_prop *prop);
> int security_inode_copy_up(struct dentry *src, struct cred **new);
> int security_inode_copy_up_xattr(struct dentry *src, const char *name);
> @@ -1077,7 +1077,8 @@ static inline int security_inode_setsecurity(struct inode *inode, const char *na
> return -EOPNOTSUPP;
> }
>
> -static inline int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size)
> +static inline int security_inode_listsecurity(struct inode *inode,
> + char **buffer, ssize_t *remaining_size)
> {
> return 0;
> }
> diff --git a/net/socket.c b/net/socket.c
> index 9a0e720f0859..52e3670dc89b 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -562,15 +562,9 @@ static ssize_t sockfs_listxattr(struct dentry *dentry, char *buffer,
> ssize_t len;
> ssize_t used = 0;
>
> - len = security_inode_listsecurity(d_inode(dentry), buffer, size);
> + len = security_inode_listsecurity(d_inode(dentry), &buffer, &used);
And likewise wrong.
> if (len < 0)
> return len;
> - used += len;
> - if (buffer) {
> - if (size < used)
> - return -ERANGE;
> - buffer += len;
> - }
>
> len = (XATTR_NAME_SOCKPROTONAME_LEN + 1);
> used += len;
> diff --git a/security/security.c b/security/security.c
> index fb57e8fddd91..3985d040d5a9 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2710,22 +2710,22 @@ int security_inode_setsecurity(struct inode *inode, const char *name,
> /**
> * security_inode_listsecurity() - List the xattr security label names
> * @inode: inode
> - * @buffer: buffer
> - * @buffer_size: size of buffer
> + * @buffer: pointer to buffer
> + * @remaining_size: pointer to remaining size of buffer
> *
> * Copy the extended attribute names for the security labels associated with
> - * @inode into @buffer. The maximum size of @buffer is specified by
> - * @buffer_size. @buffer may be NULL to request the size of the buffer
> - * required.
> + * @inode into *(@buffer). The remaining size of @buffer is specified by
> + * *(@remaining_size). *(@buffer) may be NULL to request the size of the
> + * buffer required. Updates *(@buffer) and *(@remaining_size).
> *
> - * Return: Returns number of bytes used/required on success.
> + * Return: Returns 0 on success, or -errno on failure.
> */
> int security_inode_listsecurity(struct inode *inode,
> - char *buffer, size_t buffer_size)
> + char **buffer, ssize_t *remaining_size)
> {
> if (unlikely(IS_PRIVATE(inode)))
> return 0;
> - return call_int_hook(inode_listsecurity, inode, buffer, buffer_size);
> + return call_int_hook(inode_listsecurity, inode, buffer, remaining_size);
> }
> EXPORT_SYMBOL(security_inode_listsecurity);
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index b8115df536ab..e6c98ebbf7bc 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3612,16 +3612,12 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name,
> return 0;
> }
>
> -static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size)
> +static int selinux_inode_listsecurity(struct inode *inode, char **buffer,
> + ssize_t *remaining_size)
> {
> - const int len = sizeof(XATTR_NAME_SELINUX);
> -
> if (!selinux_initialized())
> return 0;
> -
> - if (buffer && len <= buffer_size)
> - memcpy(buffer, XATTR_NAME_SELINUX, len);
> - return len;
> + return xattr_list_one(buffer, remaining_size, XATTR_NAME_SELINUX);
> }
>
> static void selinux_inode_getlsmprop(struct inode *inode, struct lsm_prop *prop)
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 99833168604e..3f7ac865532e 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1619,17 +1619,12 @@ static int smack_inode_getsecurity(struct mnt_idmap *idmap,
> * smack_inode_listsecurity - list the Smack attributes
> * @inode: the object
> * @buffer: where they go
> - * @buffer_size: size of buffer
> + * @remaining_size: size of buffer
> */
> -static int smack_inode_listsecurity(struct inode *inode, char *buffer,
> - size_t buffer_size)
> +static int smack_inode_listsecurity(struct inode *inode, char **buffer,
> + ssize_t *remaining_size)
> {
> - int len = sizeof(XATTR_NAME_SMACK);
> -
> - if (buffer != NULL && len <= buffer_size)
> - memcpy(buffer, XATTR_NAME_SMACK, len);
> -
> - return len;
> + return xattr_list_one(buffer, remaining_size, XATTR_NAME_SMACK);
> }
>
> /**
> --
> 2.49.0
>
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