[PATCH v15 14/23] LSM: Ensure the correct LSM context releaser

Casey Schaufler
2020-02-22T00:06:06Z

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>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-integrity@vger.kernel.org
Cc: netdev@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 b133f0af5151..a11e38d0cd0a 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2863,6 +2863,7 @@ 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;
@@ -3159,7 +3160,8 @@ 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;
@@ -3492,8 +3494,10 @@ 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 7b8a070a782d..9bf41894e3e1 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1272,12 +1272,16 @@ 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 95d07a3dc5d1..01cddbc7c7c0 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -130,8 +130,12 @@ 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 9761512674a0..df308b1b37fa 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2496,6 +2496,7 @@ 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
@@ -2998,8 +2999,10 @@ 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 92a783f5ae1f..80b24a034799 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -130,6 +130,37 @@ 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
*
@@ -500,7 +531,7 @@ 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);
@@ -1314,7 +1345,7 @@ 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 31ae605fcc0a..30ba801c91bd 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;
char *secdata;
u32 seclen;
int err;
@@ -102,7 +103,9 @@ 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 1bc0e1264115..ed2d8d7c6943 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1181,6 +1181,7 @@ 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)
@@ -1425,15 +1426,18 @@ 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);
@@ -2062,6 +2066,7 @@ int audit_log_task_context(struct audit_buffer *ab)
unsigned len;
int error;
struct lsmblob blob;
+ struct lsmcontext scaff; /* scaffolding */

security_task_getsecid(current, &blob);
if (!lsmblob_is_set(&blob))
@@ -2075,7 +2080,8 @@ 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 d52ae228ad3d..75bd9710790d 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -962,6 +962,7 @@ 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;
@@ -979,7 +980,8 @@ 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=");
@@ -1192,6 +1194,7 @@ 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;

@@ -1225,7 +1228,8 @@ 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) {
@@ -1371,6 +1375,7 @@ 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)) {
@@ -1379,7 +1384,8 @@ 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 1ca97d0cb4a9..96d56a30ecca 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;
@@ -144,7 +145,8 @@ 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 68c74c28eae9..3d18d6e2a7dd 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -332,6 +332,7 @@ 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(&blob, ct->secmark);
ret = security_secid_to_secctx(&blob, &secctx, &len);
@@ -349,7 +350,8 @@ 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 183a85412155..8601fcb99f7a 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 b7b296fe0c0b..8611974322b3 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -395,6 +395,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
enum ip_conntrack_info uninitialized_var(ctinfo);
struct nfnl_ct_hook *nfnl_ct;
bool csum_verify;
+ struct lsmcontext scaff; /* scaffolding */
char *secdata = NULL;
u32 seclen = 0;

@@ -625,8 +626,10 @@ 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:
@@ -634,8 +637,10 @@ 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 e279b81d9545..288c005b44c7 100644
--- a/net/netlabel/netlabel_unlabeled.c
+++ b/net/netlabel/netlabel_unlabeled.c
@@ -373,6 +373,7 @@ 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;
@@ -443,7 +444,9 @@ 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);
@@ -474,6 +477,7 @@ 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;
@@ -502,7 +506,9 @@ 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);
@@ -539,6 +545,7 @@ 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;
@@ -566,7 +573,8 @@ 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);
@@ -1080,6 +1088,7 @@ 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;
@@ -1147,7 +1156,9 @@ 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 475929e3e1e4..3a65f4ac476e 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2175,16 +2175,17 @@ 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 display = lsm_task_display(current);

hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list)
- if (display == LSMBLOB_INVALID || display == 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);