Create a new entry "display" in /proc/.../attr for controlling
which LSM security information is displayed for a process.
The name of an active LSM that supplies hooks for human readable
data may be written to "display" to set the value. This requires
CAP_MAC_ADMIN privilege. The name of the LSM currently in use can
be read from "display". At this point there can only be one LSM
capable of display active. A helper function lsm_task_display()
is provided to get the display slot for a task_struct.
Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 1 +
include/linux/lsm_hooks.h | 15 ++++
security/security.c | 139 +++++++++++++++++++++++++++++++++-----
3 files changed, 138 insertions(+), 17 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index ddef482f1334..7bf70e041315 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2618,6 +2618,7 @@ static const struct pid_entry attr_dir_stuff[] = {
ATTR(NULL, "fscreate", 0666),
ATTR(NULL, "keycreate", 0666),
ATTR(NULL, "sockcreate", 0666),
+ ATTR(NULL, "display", 0666),
#ifdef CONFIG_SECURITY_SMACK
DIR("smack", 0555,
proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index fe1fb7a69ee5..33e5ab4af9f8 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2134,4 +2134,19 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
extern int lsm_inode_alloc(struct inode *inode);
+/**
+ * lsm_task_display - the "display LSM for this task
+ * @task: The task to report on
+ *
+ * Returns the task's display LSM slot.
+ */
+static inline int lsm_task_display(struct task_struct *task)
+{
+ int *display = task->security;
+
+ if (display)
+ return *display;
+ return LSMBLOB_INVALID;
+}
+
#endif /* ! __LINUX_LSM_HOOKS_H */
diff --git a/security/security.c b/security/security.c
index 8927508b2142..cbc1c54d86c1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -31,6 +31,7 @@
#include <linux/backing-dev.h>
#include <linux/string.h>
#include <linux/msg.h>
+#include <linux/binfmts.h>
#include <net/flow.h>
#include <net/sock.h>
@@ -46,7 +47,14 @@ static struct kmem_cache *lsm_file_cache;
static struct kmem_cache *lsm_inode_cache;
char *lsm_names;
-static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init;
+
+/*
+ * The task blob includes the "display" slot used for
+ * chosing which module presents contexts.
+ */
+static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init = {
+ .lbs_task = sizeof(int),
+};
/* Boot-time LSM user choice */
static __initdata const char *chosen_lsm_order;
@@ -423,8 +431,10 @@ static int lsm_append(const char *new, char **result)
/*
* Current index to use while initializing the lsmblob secid list.
+ * Pointers to the LSM id structures for local use.
*/
static int lsm_slot __lsm_ro_after_init;
+static struct lsm_id *lsm_slotlist[LSMBLOB_ENTRIES];
/**
* security_add_hooks - Add a modules hooks to the hook lists.
@@ -444,6 +454,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
if (lsmid->slot == LSMBLOB_NEEDED) {
if (lsm_slot >= LSMBLOB_ENTRIES)
panic("%s Too many LSMs registered.\n", __func__);
+ lsm_slotlist[lsm_slot] = lsmid;
lsmid->slot = lsm_slot++;
init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm,
lsmid->slot);
@@ -564,6 +575,8 @@ int lsm_inode_alloc(struct inode *inode)
*/
static int lsm_task_alloc(struct task_struct *task)
{
+ int *display;
+
if (blob_sizes.lbs_task == 0) {
task->security = NULL;
return 0;
@@ -572,6 +585,15 @@ static int lsm_task_alloc(struct task_struct *task)
task->security = kzalloc(blob_sizes.lbs_task, GFP_KERNEL);
if (task->security == NULL)
return -ENOMEM;
+
+ /*
+ * The start of the task blob contains the "display" LSM slot number.
+ * Start with it set to the invalid slot number, indicating that the
+ * default first registered LSM be displayed.
+ */
+ display = task->security;
+ *display = LSMBLOB_INVALID;
+
return 0;
}
@@ -1563,14 +1585,26 @@ int security_file_open(struct file *file)
int security_task_alloc(struct task_struct *task, unsigned long clone_flags)
{
+ int *odisplay = current->security;
+ int *ndisplay;
int rc = lsm_task_alloc(task);
- if (rc)
+ if (unlikely(rc))
return rc;
+
rc = call_int_hook(task_alloc, 0, task, clone_flags);
- if (unlikely(rc))
+ if (unlikely(rc)) {
security_task_free(task);
- return rc;
+ return rc;
+ }
+
+ if (odisplay) {
+ ndisplay = task->security;
+ if (ndisplay)
+ *ndisplay = *odisplay;
+ }
+
+ return 0;
}
void security_task_free(struct task_struct *task)
@@ -1967,10 +2001,29 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
char **value)
{
struct security_hook_list *hp;
+ int display = lsm_task_display(current);
+ int slot = 0;
+
+ if (!strcmp(name, "display")) {
+ /*
+ * lsm_slot will be 0 if there are no displaying modules.
+ */
+ if (lsm_slot == 0)
+ return -EINVAL;
+ if (display != LSMBLOB_INVALID)
+ slot = display;
+ *value = kstrdup(lsm_slotlist[slot]->lsm, GFP_KERNEL);
+ if (*value)
+ return strlen(*value);
+ return -ENOMEM;
+ }
hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
continue;
+ if (lsm == NULL && display != LSMBLOB_INVALID &&
+ display != hp->lsmid->slot)
+ continue;
return hp->hook.getprocattr(p, name, value);
}
return -EINVAL;
@@ -1980,10 +2033,48 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
size_t size)
{
struct security_hook_list *hp;
+ char *term;
+ char *cp;
+ int *display = current->security;
+ int rc = -EINVAL;
+ int slot = 0;
+
+ if (!strcmp(name, "display")) {
+ if (!capable(CAP_MAC_ADMIN))
+ return -EPERM;
+ /*
+ * lsm_slot will be 0 if there are no displaying modules.
+ */
+ if (lsm_slot == 0 || size == 0)
+ return -EINVAL;
+ cp = kzalloc(size + 1, GFP_KERNEL);
+ if (cp == NULL)
+ return -ENOMEM;
+ memcpy(cp, value, size);
+
+ term = strchr(cp, ' ');
+ if (term == NULL)
+ term = strchr(cp, '\n');
+ if (term != NULL)
+ *term = '\0';
+
+ for (slot = 0; slot < lsm_slot; slot++)
+ if (!strcmp(cp, lsm_slotlist[slot]->lsm)) {
+ *display = lsm_slotlist[slot]->slot;
+ rc = size;
+ break;
+ }
+
+ kfree(cp);
+ return rc;
+ }
hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
continue;
+ if (lsm == NULL && *display != LSMBLOB_INVALID &&
+ *display != hp->lsmid->slot)
+ continue;
return hp->hook.setprocattr(name, value, size);
}
return -EINVAL;
@@ -2003,15 +2094,15 @@ EXPORT_SYMBOL(security_ismaclabel);
int security_secid_to_secctx(struct lsmblob *blob, char **secdata, u32 *seclen)
{
struct security_hook_list *hp;
- int rc;
+ int display = lsm_task_display(current);
hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list) {
if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
continue;
- rc = hp->hook.secid_to_secctx(blob->secid[hp->lsmid->slot],
- secdata, seclen);
- if (rc != 0)
- return rc;
+ if (display == LSMBLOB_INVALID || display == hp->lsmid->slot)
+ return hp->hook.secid_to_secctx(
+ blob->secid[hp->lsmid->slot],
+ secdata, seclen);
}
return 0;
}
@@ -2021,16 +2112,15 @@ int security_secctx_to_secid(const char *secdata, u32 seclen,
struct lsmblob *blob)
{
struct security_hook_list *hp;
- int rc;
+ int display = lsm_task_display(current);
lsmblob_init(blob, 0);
hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list) {
if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
continue;
- rc = hp->hook.secctx_to_secid(secdata, seclen,
- &blob->secid[hp->lsmid->slot]);
- if (rc != 0)
- return rc;
+ if (display == LSMBLOB_INVALID || display == hp->lsmid->slot)
+ return hp->hook.secctx_to_secid(secdata, seclen,
+ &blob->secid[hp->lsmid->slot]);
}
return 0;
}
@@ -2038,7 +2128,15 @@ EXPORT_SYMBOL(security_secctx_to_secid);
void security_release_secctx(char *secdata, u32 seclen)
{
- call_void_hook(release_secctx, secdata, seclen);
+ struct security_hook_list *hp;
+ int *display = current->security;
+
+ hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list)
+ if (display == NULL || *display == LSMBLOB_INVALID ||
+ *display == hp->lsmid->slot) {
+ hp->hook.release_secctx(secdata, seclen);
+ return;
+ }
}
EXPORT_SYMBOL(security_release_secctx);
@@ -2163,8 +2261,15 @@ EXPORT_SYMBOL(security_sock_rcv_skb);
int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
int __user *optlen, unsigned len)
{
- return call_int_hook(socket_getpeersec_stream, -ENOPROTOOPT, sock,
- optval, optlen, len);
+ int display = lsm_task_display(current);
+ struct security_hook_list *hp;
+
+ hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_stream,
+ list)
+ if (display == LSMBLOB_INVALID || display == hp->lsmid->slot)
+ return hp->hook.socket_getpeersec_stream(sock, optval,
+ optlen, len);
+ return -ENOPROTOOPT;
}
int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
--
2.20.1
