[PATCH v26 15/25] LSM: Ensure the correct LSM context releaser

Casey Schaufler
2021-05-13T20:24:57Z

Add a new lsmcontext data structure to hold all the information
about a "security context", including the string, its size and
which LSM allocated the string. The allocation information is
necessary because LSMs have different policies regarding the
lifecycle of these strings. SELinux allocates and destroys
them on each use, whereas Smack provides a pointer to an entry
in a list that never goes away.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-integrity@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-audit@redhat.com
Cc: netfilter-devel@vger.kernel.org
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: linux-nfs@vger.kernel.org
---
drivers/android/binder.c | 10 ++++---
fs/ceph/xattr.c | 6 ++++-
fs/nfs/nfs4proc.c | 8 ++++--
fs/nfsd/nfs4xdr.c | 7 +++--
include/linux/security.h | 35 +++++++++++++++++++++++--
include/net/scm.h | 5 +++-
kernel/audit.c | 14 +++++++---
kernel/auditsc.c | 12 ++++++---
net/ipv4/ip_sockglue.c | 4 ++-
net/netfilter/nf_conntrack_netlink.c | 4 ++-
net/netfilter/nf_conntrack_standalone.c | 4 ++-
net/netfilter/nfnetlink_queue.c | 13 ++++++---
net/netlabel/netlabel_unlabeled.c | 19 +++++++++++---
net/netlabel/netlabel_user.c | 4 ++-
security/security.c | 11 ++++----
15 files changed, 121 insertions(+), 35 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index ab55358f868b..eca789340ef6 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2461,6 +2461,7 @@ static void binder_transaction(struct binder_proc *proc,
int t_debug_id = atomic_inc_return(&binder_last_id);
char *secctx = NULL;
u32 secctx_sz = 0;
+ struct lsmcontext scaff; /* scaffolding */

e = binder_transaction_log_add(&binder_transaction_log);
e->debug_id = t_debug_id;
@@ -2772,7 +2773,8 @@ static void binder_transaction(struct binder_proc *proc,
t->security_ctx = 0;
WARN_ON(1);
}
- security_release_secctx(secctx, secctx_sz);
+ lsmcontext_init(&scaff, secctx, secctx_sz, 0);
+ security_release_secctx(&scaff);
secctx = NULL;
}
t->buffer->debug_id = t->debug_id;
@@ -3114,8 +3116,10 @@ static void binder_transaction(struct binder_proc *proc,
binder_alloc_free_buf(&target_proc->alloc, t->buffer);
err_binder_alloc_buf_failed:
err_bad_extra_size:
- if (secctx)
- security_release_secctx(secctx, secctx_sz);
+ if (secctx) {
+ lsmcontext_init(&scaff, secctx, secctx_sz, 0);
+ security_release_secctx(&scaff);
+ }
err_get_secctx_failed:
kfree(tcomplete);
binder_stats_deleted(BINDER_STAT_TRANSACTION_COMPLETE);
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 1242db8d3444..b867089e1aa4 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1356,12 +1356,16 @@ 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
- security_release_secctx(as_ctx->sec_ctx, as_ctx->sec_ctxlen);
+ lsmcontext_init(&scaff, as_ctx->sec_ctx, as_ctx->sec_ctxlen, 0);
+ security_release_secctx(&scaff);
#endif
if (as_ctx->pagelist)
ceph_pagelist_release(as_ctx->pagelist);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 87d04f2c9385..a179d70eeb7e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -136,8 +136,12 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
static inline void
nfs4_label_release_security(struct nfs4_label *label)
{
- if (label)
- security_release_secctx(label->label, label->len);
+ struct lsmcontext scaff; /* scaffolding */
+
+ if (label) {
+ lsmcontext_init(&scaff, label->label, label->len, 0);
+ security_release_secctx(&scaff);
+ }
}
static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
{
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 7abeccb975b2..089ec4b61ef1 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2844,6 +2844,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
int err;
struct nfs4_acl *acl = NULL;
#ifdef CONFIG_NFSD_V4_SECURITY_LABEL
+ struct lsmcontext scaff; /* scaffolding */
void *context = NULL;
int contextlen;
#endif
@@ -3345,8 +3346,10 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,

out:
#ifdef CONFIG_NFSD_V4_SECURITY_LABEL
- if (context)
- security_release_secctx(context, contextlen);
+ if (context) {
+ lsmcontext_init(&scaff, context, contextlen, 0); /*scaffolding*/
+ security_release_secctx(&scaff);
+ }
#endif /* CONFIG_NFSD_V4_SECURITY_LABEL */
kfree(acl);
if (tempfh) {
diff --git a/include/linux/security.h b/include/linux/security.h
index c1c31eb23859..3b2ffef65b05 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -133,6 +133,37 @@ enum lockdown_reason {

extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];

+/*
+ * A "security context" is the text representation of
+ * the information used by LSMs.
+ * This structure contains the string, its length, and which LSM
+ * it is useful for.
+ */
+struct lsmcontext {
+ char *context; /* Provided by the module */
+ u32 len;
+ int slot; /* 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
+ * @slot: Which LSM provided the context
+ *
+ * Fill in the lsmcontext from the provided information.
+ * This is a scaffolding function that will be removed when
+ * lsmcontext integration is complete.
+ */
+static inline void lsmcontext_init(struct lsmcontext *cp, char *context,
+ u32 size, int slot)
+{
+ cp->slot = slot;
+ cp->context = context;
+ cp->len = size;
+}
+
/*
* Data exported by the security modules
*
@@ -550,7 +581,7 @@ int security_ismaclabel(const char *name);
int security_secid_to_secctx(struct lsmblob *blob, char **secdata, u32 *seclen);
int security_secctx_to_secid(const char *secdata, u32 seclen,
struct lsmblob *blob);
-void security_release_secctx(char *secdata, u32 seclen);
+void security_release_secctx(struct lsmcontext *cp);
void security_inode_invalidate_secctx(struct inode *inode);
int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
@@ -1414,7 +1445,7 @@ static inline int security_secctx_to_secid(const char *secdata,
return -EOPNOTSUPP;
}

-static inline void security_release_secctx(char *secdata, u32 seclen)
+static inline void security_release_secctx(struct lsmcontext *cp)
{
}

diff --git a/include/net/scm.h b/include/net/scm.h
index 23a35ff1b3f2..f273c4d777ec 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -92,6 +92,7 @@ static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
#ifdef CONFIG_SECURITY_NETWORK
static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
{
+ struct lsmcontext context;
struct lsmblob lb;
char *secdata;
u32 seclen;
@@ -106,7 +107,9 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc

if (!err) {
put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
- security_release_secctx(secdata, seclen);
+ /*scaffolding*/
+ lsmcontext_init(&context, secdata, seclen, 0);
+ security_release_secctx(&context);
}
}
}
diff --git a/kernel/audit.c b/kernel/audit.c
index 8ec64e6e8bc0..c17ec23158c4 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1192,6 +1192,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
struct audit_sig_info *sig_data;
char *ctx = NULL;
u32 len;
+ struct lsmcontext scaff; /* scaffolding */

err = audit_netlink_ok(skb, msg_type);
if (err)
@@ -1449,15 +1450,18 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
}
sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
if (!sig_data) {
- if (lsmblob_is_set(&audit_sig_lsm))
- security_release_secctx(ctx, len);
+ if (lsmblob_is_set(&audit_sig_lsm)) {
+ lsmcontext_init(&scaff, ctx, len, 0);
+ security_release_secctx(&scaff);
+ }
return -ENOMEM;
}
sig_data->uid = from_kuid(&init_user_ns, audit_sig_uid);
sig_data->pid = audit_sig_pid;
if (lsmblob_is_set(&audit_sig_lsm)) {
memcpy(sig_data->ctx, ctx, len);
- security_release_secctx(ctx, len);
+ lsmcontext_init(&scaff, ctx, len, 0);
+ security_release_secctx(&scaff);
}
audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO, 0, 0,
sig_data, sizeof(*sig_data) + len);
@@ -2132,6 +2136,7 @@ int audit_log_task_context(struct audit_buffer *ab)
unsigned len;
int error;
struct lsmblob blob;
+ struct lsmcontext scaff; /* scaffolding */

security_task_getsecid_subj(current, &blob);
if (!lsmblob_is_set(&blob))
@@ -2145,7 +2150,8 @@ int audit_log_task_context(struct audit_buffer *ab)
}

audit_log_format(ab, " subj=%s", ctx);
- security_release_secctx(ctx, len);
+ lsmcontext_init(&scaff, ctx, len, 0);
+ security_release_secctx(&scaff);
return 0;

error_path:
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 573c6a8e505f..3fb9d3639123 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -996,6 +996,7 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
struct lsmblob *blob, char *comm)
{
struct audit_buffer *ab;
+ struct lsmcontext lsmcxt;
char *ctx = NULL;
u32 len;
int rc = 0;
@@ -1013,7 +1014,8 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
rc = 1;
} else {
audit_log_format(ab, " obj=%s", ctx);
- security_release_secctx(ctx, len);
+ lsmcontext_init(&lsmcxt, ctx, len, 0); /*scaffolding*/
+ security_release_secctx(&lsmcxt);
}
}
audit_log_format(ab, " ocomm=");
@@ -1226,6 +1228,7 @@ static void audit_log_fcaps(struct audit_buffer *ab, struct audit_names *name)

static void show_special(struct audit_context *context, int *call_panic)
{
+ struct lsmcontext lsmcxt;
struct audit_buffer *ab;
int i;

@@ -1259,7 +1262,8 @@ static void show_special(struct audit_context *context, int *call_panic)
*call_panic = 1;
} else {
audit_log_format(ab, " obj=%s", ctx);
- security_release_secctx(ctx, len);
+ lsmcontext_init(&lsmcxt, ctx, len, 0);
+ security_release_secctx(&lsmcxt);
}
}
if (context->ipc.has_perm) {
@@ -1408,6 +1412,7 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
char *ctx = NULL;
u32 len;
struct lsmblob blob;
+ struct lsmcontext lsmcxt;

lsmblob_init(&blob, n->osid);
if (security_secid_to_secctx(&blob, &ctx, &len)) {
@@ -1416,7 +1421,8 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
*call_panic = 2;
} else {
audit_log_format(ab, " obj=%s", ctx);
- security_release_secctx(ctx, len);
+ lsmcontext_init(&lsmcxt, ctx, len, 0); /* scaffolding */
+ security_release_secctx(&lsmcxt);
}
}

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 2f089733ada7..a7e4c1b34b6c 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -130,6 +130,7 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,

static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
{
+ struct lsmcontext context;
struct lsmblob lb;
char *secdata;
u32 seclen, secid;
@@ -145,7 +146,8 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
return;

put_cmsg(msg, SOL_IP, SCM_SECURITY, seclen, secdata);
- security_release_secctx(secdata, seclen);
+ lsmcontext_init(&context, secdata, seclen, 0); /* scaffolding */
+ security_release_secctx(&context);
}

static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index caf3ecb5a66b..914ab6a96573 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -339,6 +339,7 @@ static int ctnetlink_dump_secctx(struct sk_buff *skb, const struct nf_conn *ct)
int len, ret;
char *secctx;
struct lsmblob blob;
+ struct lsmcontext context;

/* lsmblob_init() puts ct->secmark into all of the secids in blob.
* security_secid_to_secctx() will know which security module
@@ -359,7 +360,8 @@ static int ctnetlink_dump_secctx(struct sk_buff *skb, const struct nf_conn *ct)

ret = 0;
nla_put_failure:
- security_release_secctx(secctx, len);
+ lsmcontext_init(&context, secctx, len, 0); /* scaffolding */
+ security_release_secctx(&context);
return ret;
}
#else
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index b02afa0a1516..b039445f3efc 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -176,6 +176,7 @@ static void ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
u32 len;
char *secctx;
struct lsmblob blob;
+ struct lsmcontext context;

lsmblob_init(&blob, ct->secmark);
ret = security_secid_to_secctx(&blob, &secctx, &len);
@@ -184,7 +185,8 @@ static void ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)

seq_printf(s, "secctx=%s ", secctx);

- security_release_secctx(secctx, len);
+ lsmcontext_init(&context, secctx, len, 0); /* scaffolding */
+ security_release_secctx(&context);
}
#else
static inline void ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index bdbb0b60bf7b..06b7751c7668 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -397,6 +397,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
enum ip_conntrack_info ctinfo;
struct nfnl_ct_hook *nfnl_ct;
bool csum_verify;
+ struct lsmcontext scaff; /* scaffolding */
char *secdata = NULL;
u32 seclen = 0;

@@ -626,8 +627,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
}

nlh->nlmsg_len = skb->len;
- if (seclen)
- security_release_secctx(secdata, seclen);
+ if (seclen) {
+ lsmcontext_init(&scaff, secdata, seclen, 0);
+ security_release_secctx(&scaff);
+ }
return skb;

nla_put_failure:
@@ -635,8 +638,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
kfree_skb(skb);
net_err_ratelimited("nf_queue: error creating packet message\n");
nlmsg_failure:
- if (seclen)
- security_release_secctx(secdata, seclen);
+ if (seclen) {
+ lsmcontext_init(&scaff, secdata, seclen, 0);
+ security_release_secctx(&scaff);
+ }
return NULL;
}

diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
index b08442582874..8ca1e2b33dcf 100644
--- a/net/netlabel/netlabel_unlabeled.c
+++ b/net/netlabel/netlabel_unlabeled.c
@@ -374,6 +374,7 @@ int netlbl_unlhsh_add(struct net *net,
struct net_device *dev;
struct netlbl_unlhsh_iface *iface;
struct audit_buffer *audit_buf = NULL;
+ struct lsmcontext context;
char *secctx = NULL;
u32 secctx_len;
struct lsmblob blob;
@@ -447,7 +448,9 @@ int netlbl_unlhsh_add(struct net *net,
&secctx,
&secctx_len) == 0) {
audit_log_format(audit_buf, " sec_obj=%s", secctx);
- security_release_secctx(secctx, secctx_len);
+ /* scaffolding */
+ lsmcontext_init(&context, secctx, secctx_len, 0);
+ security_release_secctx(&context);
}
audit_log_format(audit_buf, " res=%u", ret_val == 0 ? 1 : 0);
audit_log_end(audit_buf);
@@ -478,6 +481,7 @@ static int netlbl_unlhsh_remove_addr4(struct net *net,
struct netlbl_unlhsh_addr4 *entry;
struct audit_buffer *audit_buf;
struct net_device *dev;
+ struct lsmcontext context;
char *secctx;
u32 secctx_len;
struct lsmblob blob;
@@ -509,7 +513,9 @@ static int netlbl_unlhsh_remove_addr4(struct net *net,
security_secid_to_secctx(&blob,
&secctx, &secctx_len) == 0) {
audit_log_format(audit_buf, " sec_obj=%s", secctx);
- security_release_secctx(secctx, secctx_len);
+ /* scaffolding */
+ lsmcontext_init(&context, secctx, secctx_len, 0);
+ security_release_secctx(&context);
}
audit_log_format(audit_buf, " res=%u", entry != NULL ? 1 : 0);
audit_log_end(audit_buf);
@@ -546,6 +552,7 @@ static int netlbl_unlhsh_remove_addr6(struct net *net,
struct netlbl_unlhsh_addr6 *entry;
struct audit_buffer *audit_buf;
struct net_device *dev;
+ struct lsmcontext context;
char *secctx;
u32 secctx_len;
struct lsmblob blob;
@@ -576,7 +583,8 @@ static int netlbl_unlhsh_remove_addr6(struct net *net,
security_secid_to_secctx(&blob,
&secctx, &secctx_len) == 0) {
audit_log_format(audit_buf, " sec_obj=%s", secctx);
- security_release_secctx(secctx, secctx_len);
+ lsmcontext_init(&context, secctx, secctx_len, 0);
+ security_release_secctx(&context);
}
audit_log_format(audit_buf, " res=%u", entry != NULL ? 1 : 0);
audit_log_end(audit_buf);
@@ -1095,6 +1103,7 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd,
int ret_val = -ENOMEM;
struct netlbl_unlhsh_walk_arg *cb_arg = arg;
struct net_device *dev;
+ struct lsmcontext context;
void *data;
u32 secid;
char *secctx;
@@ -1165,7 +1174,9 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd,
NLBL_UNLABEL_A_SECCTX,
secctx_len,
secctx);
- security_release_secctx(secctx, secctx_len);
+ /* scaffolding */
+ lsmcontext_init(&context, secctx, secctx_len, 0);
+ security_release_secctx(&context);
if (ret_val != 0)
goto list_cb_failure;

diff --git a/net/netlabel/netlabel_user.c b/net/netlabel/netlabel_user.c
index 893301ae0131..ef139d8ae7cd 100644
--- a/net/netlabel/netlabel_user.c
+++ b/net/netlabel/netlabel_user.c
@@ -84,6 +84,7 @@ struct audit_buffer *netlbl_audit_start_common(int type,
struct netlbl_audit *audit_info)
{
struct audit_buffer *audit_buf;
+ struct lsmcontext context;
char *secctx;
u32 secctx_len;
struct lsmblob blob;
@@ -103,7 +104,8 @@ struct audit_buffer *netlbl_audit_start_common(int type,
if (audit_info->secid != 0 &&
security_secid_to_secctx(&blob, &secctx, &secctx_len) == 0) {
audit_log_format(audit_buf, " subj=%s", secctx);
- security_release_secctx(secctx, secctx_len);
+ lsmcontext_init(&context, secctx, secctx_len, 0);/*scaffolding*/
+ security_release_secctx(&context);
}

return audit_buf;
diff --git a/security/security.c b/security/security.c
index 1ce125c01782..f6a33bf2a7fc 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2359,16 +2359,17 @@ int security_secctx_to_secid(const char *secdata, u32 seclen,
}
EXPORT_SYMBOL(security_secctx_to_secid);

-void security_release_secctx(char *secdata, u32 seclen)
+void security_release_secctx(struct lsmcontext *cp)
{
struct security_hook_list *hp;
- int ilsm = lsm_task_ilsm(current);

hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list)
- if (ilsm == LSMBLOB_INVALID || ilsm == hp->lsmid->slot) {
- hp->hook.release_secctx(secdata, seclen);
- return;
+ if (cp->slot == hp->lsmid->slot) {
+ hp->hook.release_secctx(cp->context, cp->len);
+ break;
}
+
+ memset(cp, 0, sizeof(*cp));
}
EXPORT_SYMBOL(security_release_secctx);

--
2.29.2