[PATCH v2 4/6] LSM: lsm_context in security_dentry_init_security

From: Casey Schaufler
Date: Mon Oct 14 2024 - 11:20:51 EST

Replace the (secctx,seclen) pointer pair with a single lsm_context
pointer to allow return of the LSM identifier along with the context
and context length. This allows security_release_secctx() to know how
to release the context. Callers have been modified to use or save the
returned data from the new structure.

Special care is taken in the NFS code, which uses the same data structure
for its own copied labels as it does for the data which comes from
security_dentry_init_security(). In the case of copied labels the data
has to be freed, not released.

The scaffolding funtion lsmcontext_init() is no longer needed and is
removed.

Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Cc: ceph-devel@xxxxxxxxxxxxxxx
Cc: linux-nfs@xxxxxxxxxxxxxxx
---
fs/ceph/super.h | 3 +--
fs/ceph/xattr.c | 16 ++++++----------
fs/fuse/dir.c | 35 ++++++++++++++++++-----------------
fs/nfs/dir.c | 2 +-
fs/nfs/inode.c | 17 ++++++++++-------
fs/nfs/internal.h | 8 +++++---
fs/nfs/nfs4proc.c | 22 +++++++++-------------
fs/nfs/nfs4xdr.c | 22 ++++++++++++----------
include/linux/lsm_hook_defs.h | 2 +-
include/linux/nfs4.h | 8 ++++----
include/linux/nfs_fs.h | 2 +-
include/linux/security.h | 26 +++-----------------------
security/security.c | 9 ++++-----
security/selinux/hooks.c | 9 +++++----
14 files changed, 80 insertions(+), 101 deletions(-)

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 2508aa8950b7..c9fad8c825dd 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -1133,8 +1133,7 @@ struct ceph_acl_sec_ctx {
void *acl;
#endif
#ifdef CONFIG_CEPH_FS_SECURITY_LABEL
- void *sec_ctx;
- u32 sec_ctxlen;
+ struct lsm_context lsmctx;
#endif
#ifdef CONFIG_FS_ENCRYPTION
struct ceph_fscrypt_auth *fscrypt_auth;
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index f7996770cc2c..0b9e1f385d31 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1383,8 +1383,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
int err;

err = security_dentry_init_security(dentry, mode, &dentry->d_name,
- &name, &as_ctx->sec_ctx,
- &as_ctx->sec_ctxlen);
+ &name, &as_ctx->lsmctx);
if (err < 0) {
WARN_ON_ONCE(err != -EOPNOTSUPP);
err = 0; /* do nothing */
@@ -1409,7 +1408,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
*/
name_len = strlen(name);
err = ceph_pagelist_reserve(pagelist,
- 4 * 2 + name_len + as_ctx->sec_ctxlen);
+ 4 * 2 + name_len + as_ctx->lsmctx.len);
if (err)
goto out;

@@ -1432,8 +1431,9 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
ceph_pagelist_encode_32(pagelist, name_len);
ceph_pagelist_append(pagelist, name, name_len);

- ceph_pagelist_encode_32(pagelist, as_ctx->sec_ctxlen);
- ceph_pagelist_append(pagelist, as_ctx->sec_ctx, as_ctx->sec_ctxlen);
+ ceph_pagelist_encode_32(pagelist, as_ctx->lsmctx.len);
+ ceph_pagelist_append(pagelist, as_ctx->lsmctx.context,
+ as_ctx->lsmctx.len);

err = 0;
out:
@@ -1446,16 +1446,12 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,

void ceph_release_acl_sec_ctx(struct ceph_acl_sec_ctx *as_ctx)
{
-#ifdef CONFIG_CEPH_FS_SECURITY_LABEL
- struct lsm_context scaff; /* scaffolding */
-#endif
#ifdef CONFIG_CEPH_FS_POSIX_ACL
posix_acl_release(as_ctx->acl);
posix_acl_release(as_ctx->default_acl);
#endif
#ifdef CONFIG_CEPH_FS_SECURITY_LABEL
- lsmcontext_init(&scaff, as_ctx->sec_ctx, as_ctx->sec_ctxlen, 0);
- security_release_secctx(&scaff);
+ security_release_secctx(&as_ctx->lsmctx);
#endif
#ifdef CONFIG_FS_ENCRYPTION
kfree(as_ctx->fscrypt_auth);
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 54104dd48af7..eea4d0d27ce1 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -466,29 +466,29 @@ static int get_security_context(struct dentry *entry, umode_t mode,
{
struct fuse_secctx *fctx;
struct fuse_secctx_header *header;
- void *ctx = NULL, *ptr;
- u32 ctxlen, total_len = sizeof(*header);
+ struct lsm_context lsmctx = { };
+ void *ptr;
+ u32 total_len = sizeof(*header);
int err, nr_ctx = 0;
- const char *name;
+ const char *name = NULL;
size_t namelen;

err = security_dentry_init_security(entry, mode, &entry->d_name,
- &name, &ctx, &ctxlen);
- if (err) {
- if (err != -EOPNOTSUPP)
- goto out_err;
- /* No LSM is supporting this security hook. Ignore error */
- ctxlen = 0;
- ctx = NULL;
- }
+ &name, &lsmctx);
+
+ /* If no LSM is supporting this security hook ignore error */
+ if (err && err != -EOPNOTSUPP)
+ goto out_err;

- if (ctxlen) {
+ if (lsmctx.len) {
nr_ctx = 1;
namelen = strlen(name) + 1;
err = -EIO;
- if (WARN_ON(namelen > XATTR_NAME_MAX + 1 || ctxlen > S32_MAX))
+ if (WARN_ON(namelen > XATTR_NAME_MAX + 1 ||
+ lsmctx.len > S32_MAX))
goto out_err;
- total_len += FUSE_REC_ALIGN(sizeof(*fctx) + namelen + ctxlen);
+ total_len += FUSE_REC_ALIGN(sizeof(*fctx) + namelen +
+ lsmctx.len);
}

err = -ENOMEM;
@@ -501,19 +501,20 @@ static int get_security_context(struct dentry *entry, umode_t mode,
ptr += sizeof(*header);
if (nr_ctx) {
fctx = ptr;
- fctx->size = ctxlen;
+ fctx->size = lsmctx.len;
ptr += sizeof(*fctx);

strcpy(ptr, name);
ptr += namelen;

- memcpy(ptr, ctx, ctxlen);
+ memcpy(ptr, lsmctx.context, lsmctx.len);
}
ext->size = total_len;
ext->value = header;
err = 0;
out_err:
- kfree(ctx);
+ if (nr_ctx)
+ security_release_secctx(&lsmctx);
return err;
}

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 492cffd9d3d8..1813ad9e9320 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -809,7 +809,7 @@ static int nfs_readdir_entry_decode(struct nfs_readdir_descriptor *desc,
int ret;

if (entry->fattr->label)
- entry->fattr->label->len = NFS4_MAXLABELLEN;
+ entry->fattr->label->lsmctx.len = NFS4_MAXLABELLEN;
ret = xdr_decode(desc, entry, stream);
if (ret || !desc->plus)
return ret;
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 542c7d97b235..d00a6304133a 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -358,14 +358,15 @@ void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr)
return;

if ((fattr->valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL) && inode->i_security) {
- error = security_inode_notifysecctx(inode, fattr->label->label,
- fattr->label->len);
+ error = security_inode_notifysecctx(inode,
+ fattr->label->lsmctx.context,
+ fattr->label->lsmctx.len);
if (error)
printk(KERN_ERR "%s() %s %d "
"security_inode_notifysecctx() %d\n",
__func__,
- (char *)fattr->label->label,
- fattr->label->len, error);
+ (char *)fattr->label->lsmctx.context,
+ fattr->label->lsmctx.len, error);
nfs_clear_label_invalid(inode);
}
}
@@ -381,12 +382,14 @@ struct nfs4_label *nfs4_label_alloc(struct nfs_server *server, gfp_t flags)
if (label == NULL)
return ERR_PTR(-ENOMEM);

- label->label = kzalloc(NFS4_MAXLABELLEN, flags);
- if (label->label == NULL) {
+ label->lsmctx.context = kzalloc(NFS4_MAXLABELLEN, flags);
+ if (label->lsmctx.context == NULL) {
kfree(label);
return ERR_PTR(-ENOMEM);
}
- label->len = NFS4_MAXLABELLEN;
+ label->lsmctx.len = NFS4_MAXLABELLEN;
+ /* Use an invalid LSM ID as this should never be "released". */
+ label->lsmctx.id = LSM_ID_UNDEF;

return label;
}
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 430733e3eff2..96477a57f65a 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -355,13 +355,15 @@ nfs4_label_copy(struct nfs4_label *dst, struct nfs4_label *src)
if (!dst || !src)
return NULL;

- if (src->len > NFS4_MAXLABELLEN)
+ if (src->lsmctx.len > NFS4_MAXLABELLEN)
return NULL;

dst->lfs = src->lfs;
dst->pi = src->pi;
- dst->len = src->len;
- memcpy(dst->label, src->label, src->len);
+ /* Use an invalid LSM ID as lsmctx should never be "released" */
+ dst->lsmctx.id = LSM_ID_UNDEF;
+ dst->lsmctx.len = src->lsmctx.len;
+ memcpy(dst->lsmctx.context, src->lsmctx.context, src->lsmctx.len);

return dst;
}
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 76776d716744..b07d01f390dc 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -124,12 +124,11 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,

label->lfs = 0;
label->pi = 0;
- label->len = 0;
- label->label = NULL;
+ label->lsmctx.len = 0;
+ label->lsmctx.context = NULL;

err = security_dentry_init_security(dentry, sattr->ia_mode,
- &dentry->d_name, NULL,
- (void **)&label->label, &label->len);
+ &dentry->d_name, NULL, &label->lsmctx);
if (err == 0)
return label;

@@ -138,12 +137,8 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
static inline void
nfs4_label_release_security(struct nfs4_label *label)
{
- struct lsm_context scaff; /* scaffolding */
-
- if (label) {
- lsmcontext_init(&scaff, label->label, label->len, 0);
- security_release_secctx(&scaff);
- }
+ if (label)
+ security_release_secctx(&label->lsmctx);
}
static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
{
@@ -6259,7 +6254,7 @@ static int _nfs4_get_security_label(struct inode *inode, void *buf,
size_t buflen)
{
struct nfs_server *server = NFS_SERVER(inode);
- struct nfs4_label label = {0, 0, buflen, buf};
+ struct nfs4_label label = {0, 0, {buf, buflen, -1} };

u32 bitmask[3] = { 0, 0, FATTR4_WORD2_SECURITY_LABEL };
struct nfs_fattr fattr = {
@@ -6287,7 +6282,7 @@ static int _nfs4_get_security_label(struct inode *inode, void *buf,
return ret;
if (!(fattr.valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL))
return -ENOENT;
- return label.len;
+ return label.lsmctx.len;
}

static int nfs4_get_security_label(struct inode *inode, void *buf,
@@ -6364,7 +6359,8 @@ static int nfs4_do_set_security_label(struct inode *inode,
static int
nfs4_set_security_label(struct inode *inode, const void *buf, size_t buflen)
{
- struct nfs4_label ilabel = {0, 0, buflen, (char *)buf };
+ struct nfs4_label ilabel = {0, 0,
+ {(char *)buf, buflen, -1}};
struct nfs_fattr *fattr;
int status;

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index e8ac3f615f93..61a2b0e61c66 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -1154,7 +1154,7 @@ static void encode_attrs(struct xdr_stream *xdr, const struct iattr *iap,
}

if (label && (attrmask[2] & FATTR4_WORD2_SECURITY_LABEL)) {
- len += 4 + 4 + 4 + (XDR_QUADLEN(label->len) << 2);
+ len += 4 + 4 + 4 + (XDR_QUADLEN(label->lsmctx.len) << 2);
bmval[2] |= FATTR4_WORD2_SECURITY_LABEL;
}

@@ -1186,8 +1186,9 @@ static void encode_attrs(struct xdr_stream *xdr, const struct iattr *iap,
if (label && (bmval[2] & FATTR4_WORD2_SECURITY_LABEL)) {
*p++ = cpu_to_be32(label->lfs);
*p++ = cpu_to_be32(label->pi);
- *p++ = cpu_to_be32(label->len);
- p = xdr_encode_opaque_fixed(p, label->label, label->len);
+ *p++ = cpu_to_be32(label->lsmctx.len);
+ p = xdr_encode_opaque_fixed(p, label->lsmctx.context,
+ label->lsmctx.len);
}
if (bmval[2] & FATTR4_WORD2_MODE_UMASK) {
*p++ = cpu_to_be32(iap->ia_mode & S_IALLUGO);
@@ -4272,11 +4273,11 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
return -EIO;
bitmap[2] &= ~FATTR4_WORD2_SECURITY_LABEL;
if (len < NFS4_MAXLABELLEN) {
- if (label && label->len) {
- if (label->len < len)
+ if (label && label->lsmctx.len) {
+ if (label->lsmctx.len < len)
return -ERANGE;
- memcpy(label->label, p, len);
- label->len = len;
+ memcpy(label->lsmctx.context, p, len);
+ label->lsmctx.len = len;
label->pi = pi;
label->lfs = lfs;
status = NFS_ATTR_FATTR_V4_SECURITY_LABEL;
@@ -4284,10 +4285,11 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
} else
printk(KERN_WARNING "%s: label too long (%u)!\n",
__func__, len);
- if (label && label->label)
+ if (label && label->lsmctx.context)
dprintk("%s: label=%.*s, len=%d, PI=%d, LFS=%d\n",
- __func__, label->len, (char *)label->label,
- label->len, label->pi, label->lfs);
+ __func__, label->lsmctx.len,
+ (char *)label->lsmctx.context,
+ label->lsmctx.len, label->pi, label->lfs);
}
return status;
}
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 69e1076448c6..e2f1ce37c41e 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -83,7 +83,7 @@ LSM_HOOK(int, 0, move_mount, const struct path *from_path,
const struct path *to_path)
LSM_HOOK(int, -EOPNOTSUPP, dentry_init_security, struct dentry *dentry,
int mode, const struct qstr *name, const char **xattr_name,
- void **ctx, u32 *ctxlen)
+ struct lsm_context *cp)
LSM_HOOK(int, 0, dentry_create_files_as, struct dentry *dentry, int mode,
struct qstr *name, const struct cred *old, struct cred *new)

diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index 8d7430d9f218..22032b0f6022 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -15,6 +15,7 @@

#include <linux/list.h>
#include <linux/uidgid.h>
+#include <linux/security.h>
#include <uapi/linux/nfs4.h>
#include <linux/sunrpc/msg_prot.h>

@@ -44,10 +45,9 @@ struct nfs4_acl {
#define NFS4_MAXLABELLEN 2048

struct nfs4_label {
- uint32_t lfs;
- uint32_t pi;
- u32 len;
- char *label;
+ uint32_t lfs;
+ uint32_t pi;
+ struct lsm_context lsmctx;
};

typedef struct { char data[NFS4_VERIFIER_SIZE]; } nfs4_verifier;
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 039898d70954..47652d217d05 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -457,7 +457,7 @@ static inline void nfs4_label_free(struct nfs4_label *label)
{
#ifdef CONFIG_NFS_V4_SECURITY_LABEL
if (label) {
- kfree(label->label);
+ kfree(label->lsmctx.context);
kfree(label);
}
#endif
diff --git a/include/linux/security.h b/include/linux/security.h
index 7d0adc1833ab..3ad59666e56c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -237,25 +237,6 @@ struct lsm_context {
int id; /* Identifies the module */
};

-/**
- * lsmcontext_init - initialize an lsmcontext structure.
- * @cp: Pointer to the context to initialize
- * @context: Initial context, or NULL
- * @size: Size of context, or 0
- * @id: Which LSM provided the context
- *
- * Fill in the lsmcontext from the provided information.
- * This is a scaffolding function that will be removed when
- * lsm_context integration is complete.
- */
-static inline void lsmcontext_init(struct lsm_context *cp, char *context,
- u32 size, int id)
-{
- cp->id = id;
- cp->context = context;
- cp->len = size;
-}
-
/*
* Values used in the task_security_ops calls
*/
@@ -409,8 +390,8 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb,
int security_move_mount(const struct path *from_path, const struct path *to_path);
int security_dentry_init_security(struct dentry *dentry, int mode,
const struct qstr *name,
- const char **xattr_name, void **ctx,
- u32 *ctxlen);
+ const char **xattr_name,
+ struct lsm_context *lsmcxt);
int security_dentry_create_files_as(struct dentry *dentry, int mode,
struct qstr *name,
const struct cred *old,
@@ -883,8 +864,7 @@ static inline int security_dentry_init_security(struct dentry *dentry,
int mode,
const struct qstr *name,
const char **xattr_name,
- void **ctx,
- u32 *ctxlen)
+ struct lsm_context *lsmcxt)
{
return -EOPNOTSUPP;
}
diff --git a/security/security.c b/security/security.c
index 4ca3c9e28b6f..1d57e4e1bceb 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1734,8 +1734,7 @@ void security_inode_free(struct inode *inode)
* @mode: mode used to determine resource type
* @name: name of the last path component
* @xattr_name: name of the security/LSM xattr
- * @ctx: pointer to the resulting LSM context
- * @ctxlen: length of @ctx
+ * @lsmctx: pointer to the resulting LSM context
*
* Compute a context for a dentry as the inode is not yet available since NFSv4
* has no label backed by an EA anyway. It is important to note that
@@ -1745,11 +1744,11 @@ void security_inode_free(struct inode *inode)
*/
int security_dentry_init_security(struct dentry *dentry, int mode,
const struct qstr *name,
- const char **xattr_name, void **ctx,
- u32 *ctxlen)
+ const char **xattr_name,
+ struct lsm_context *lsmctx)
{
return call_int_hook(dentry_init_security, dentry, mode, name,
- xattr_name, ctx, ctxlen);
+ xattr_name, lsmctx);
}
EXPORT_SYMBOL(security_dentry_init_security);

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ce5e45abd8d3..79776a5e651d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2869,8 +2869,8 @@ static void selinux_inode_free_security(struct inode *inode)

static int selinux_dentry_init_security(struct dentry *dentry, int mode,
const struct qstr *name,
- const char **xattr_name, void **ctx,
- u32 *ctxlen)
+ const char **xattr_name,
+ struct lsm_context *cp)
{
u32 newsid;
int rc;
@@ -2885,8 +2885,9 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode,
if (xattr_name)
*xattr_name = XATTR_NAME_SELINUX;

- return security_sid_to_context(newsid, (char **)ctx,
- ctxlen);
+ cp->id = LSM_ID_SELINUX;
+ return security_sid_to_context(newsid, (char **)cp->context,
+ &cp->len);
}

static int selinux_dentry_create_files_as(struct dentry *dentry, int mode,
--
2.46.0