[PATCH v37 18/33] LSM: Use lsmcontext in security_dentry_init_security

From: Casey Schaufler
Date: Mon Jun 27 2022 - 21:09:03 EST

Replace the (secctx,seclen) pointer pair with a single
lsmcontext 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.

Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
---
fs/ceph/super.h | 3 +--
fs/ceph/xattr.c | 19 ++++++-------------
fs/fuse/dir.c | 35 ++++++++++++++++++-----------------
fs/nfs/dir.c | 2 +-
fs/nfs/inode.c | 17 ++++++++++-------
fs/nfs/internal.h | 8 +++++---
fs/nfs/nfs4proc.c | 20 ++++++++------------
fs/nfs/nfs4xdr.c | 22 ++++++++++++----------
include/linux/nfs4.h | 8 ++++----
include/linux/nfs_fs.h | 2 +-
include/linux/security.h | 18 ++++++++++++++----
security/security.c | 26 +++++++++++++++++++-------
12 files changed, 99 insertions(+), 81 deletions(-)

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index f59dac66955b..e76967c7b69c 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -1059,8 +1059,7 @@ struct ceph_acl_sec_ctx {
void *acl;
#endif
#ifdef CONFIG_CEPH_FS_SECURITY_LABEL
- void *sec_ctx;
- u32 sec_ctxlen;
+ struct lsmcontext lsmctx;
#endif
struct ceph_pagelist *pagelist;
};
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 4c4dad4713b6..0068ee3bd13a 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1328,8 +1328,7 @@ 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 */
@@ -1354,7 +1353,7 @@ 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;

@@ -1374,11 +1373,9 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
as_ctx->pagelist = pagelist;
}

- 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:
@@ -1391,16 +1388,12 @@ 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 lsmcontext 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
if (as_ctx->pagelist)
ceph_pagelist_release(as_ctx->pagelist);
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 74303d6e987b..ede296af6898 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -464,29 +464,29 @@ 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 lsmcontext 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;
@@ -499,19 +499,20 @@ 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);
}
*security_ctxlen = total_len;
*security_ctx = 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 0c4e8dd6aa96..861d23eeac6e 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -810,7 +810,7 @@ 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 b4e46b0ffa2d..d3132f4626d0 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -361,14 +361,15 @@ 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);
}
}
@@ -384,12 +385,14 @@ 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 slot as this should never be "released". */
+ label->lsmctx.slot = -1;

return label;
}
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 8f8cd6e2d4db..b97b66b8b7d0 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -342,13 +342,15 @@ 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 slot as lsmctx should never be "released" */
+ dst->lsmctx.slot = -1;
+ 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 d6bdb0868729..dca0d5c84337 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -123,8 +123,7 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
return 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;

@@ -133,12 +132,8 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
static inline void
nfs4_label_release_security(struct nfs4_label *label)
{
- struct lsmcontext 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)
{
@@ -3800,7 +3795,7 @@ nfs4_atomic_open(struct inode *dir, struct nfs_open_context *ctx,
int open_flags, struct iattr *attr, int *opened)
{
struct nfs4_state *state;
- struct nfs4_label l = {0, 0, 0, NULL}, *label = NULL;
+ struct nfs4_label l = { }, *label = NULL;

label = nfs4_label_init_security(dir, ctx->dentry, attr, &l);

@@ -6108,7 +6103,7 @@ 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 = {
@@ -6136,7 +6131,7 @@ 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,
@@ -6213,7 +6208,8 @@ 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 acfe5f4bda48..9f1a376fb92c 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);
@@ -4236,12 +4237,12 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
return -EIO;
if (len < NFS4_MAXLABELLEN) {
if (label) {
- if (label->len) {
- if (label->len < len)
+ if (label->lsmctx.len) {
+ if (label->lsmctx.len < len)
return -ERANGE;
- memcpy(label->label, p, len);
+ memcpy(label->lsmctx.context, p, len);
}
- label->len = len;
+ label->lsmctx.len = len;
label->pi = pi;
label->lfs = lfs;
status = NFS_ATTR_FATTR_V4_SECURITY_LABEL;
@@ -4250,10 +4251,11 @@ 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/nfs4.h b/include/linux/nfs4.h
index 8d04b6a5964c..5c2d69cf609a 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 lsmcontext 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 a17c337dbdf1..a838d4a45c1b 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -428,7 +428,7 @@ 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 ca2ed1909608..a4d08b47cbc3 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -229,8 +229,19 @@ static inline bool lsmblob_equal(const struct lsmblob *bloba,
}

/* Map lsm names to blob slot numbers */
+#if LSMBLOB_ENTRIES > 0
extern int lsm_name_to_slot(char *name);
extern const char *lsm_slot_to_name(int slot);
+#else
+static inline int lsm_name_to_slot(char *name)
+{
+ return LSMBLOB_INVALID;
+}
+static inline const char *lsm_slot_to_name(int slot)
+{
+ return NULL;
+}
+#endif

/**
* lsmblob_value - find the first non-zero value in an lsmblob structure.
@@ -470,8 +481,8 @@ 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 lsmcontext *lsmcxt);
int security_dentry_create_files_as(struct dentry *dentry, int mode,
struct qstr *name,
const struct cred *old,
@@ -888,8 +899,7 @@ 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 lsmcontext *lsmcxt)
{
return -EOPNOTSUPP;
}
diff --git a/security/security.c b/security/security.c
index 72df3d0cd233..96a89fd5802b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -487,6 +487,8 @@ static int lsm_append(const char *new, char **result)
* Current index to use while initializing the lsmblob secid list.
*/
static int lsm_slot __lsm_ro_after_init;
+
+#if LSMBLOB_ENTRIES > 0
static struct lsm_id *lsm_slotlist[LSMBLOB_ENTRIES] __lsm_ro_after_init;

/**
@@ -531,6 +533,7 @@ const char *lsm_slot_to_name(int slot)
return NULL;
return lsm_slotlist[slot]->lsm;
}
+#endif /* LSMBLOB_ENTRIES > 0 */

/**
* security_add_hooks - Add a modules hooks to the hook lists.
@@ -549,6 +552,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,

WARN_ON(!lsmid->slot || !lsmid->lsm);

+#if LSMBLOB_ENTRIES > 0
if (lsmid->slot == LSMBLOB_NEEDED) {
if (lsm_slot >= LSMBLOB_ENTRIES)
panic("%s Too many LSMs registered.\n", __func__);
@@ -557,6 +561,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm,
lsmid->slot);
}
+#endif /* LSMBLOB_ENTRIES > 0 */

for (i = 0; i < count; i++) {
hooks[i].lsmid = lsmid;
@@ -1167,8 +1172,8 @@ 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 lsmcontext *lsmctx)
{
struct security_hook_list *hp;
int rc;
@@ -1176,9 +1181,13 @@ int security_dentry_init_security(struct dentry *dentry, int mode,
/*
* Only one module will provide a security context.
*/
- hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security, list) {
+ hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security,
+ list) {
rc = hp->hook.dentry_init_security(dentry, mode, name,
- xattr_name, ctx, ctxlen);
+ xattr_name,
+ (void **)&lsmctx->context,
+ &lsmctx->len);
+ lsmctx->slot = hp->lsmid->slot;
if (rc != LSM_RET_DEFAULT(dentry_init_security))
return rc;
}
@@ -2238,7 +2247,7 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
ilsm = lsm_task_ilsm(p);
if (ilsm != LSMBLOB_INVALID)
slot = ilsm;
- *value = kstrdup(lsm_slotlist[slot]->lsm, GFP_KERNEL);
+ *value = kstrdup(lsm_slot_to_name(slot), GFP_KERNEL);
if (*value)
return strlen(*value);
return -ENOMEM;
@@ -2273,6 +2282,7 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
size_t size)
{
struct security_hook_list *hp;
+ const char *slotname;
char *termed;
char *copy;
int *ilsm = current->security;
@@ -2304,12 +2314,14 @@ int security_setprocattr(const char *lsm, const char *name, void *value,

termed = strsep(&copy, " \n");

- for (slot = 0; slot < lsm_slot; slot++)
+ for (slot = 0; slot < lsm_slot; slot++) {
+ slotname = lsm_slot_to_name(slot);
if (!strcmp(termed, lsm_slotlist[slot]->lsm)) {
- *ilsm = lsm_slotlist[slot]->slot;
+ *ilsm = slot;
rc = size;
break;
}
+ }

kfree(termed);
return rc;
--
2.36.1