On 6/26/19 12:22 PM, Casey Schaufler wrote:
> 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. 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.
>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Reviewed-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> ---
> fs/proc/base.c | 1 +
> security/security.c | 129 ++++++++++++++++++++++++++++++++++++++------
> 2 files changed, 113 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/security/security.c b/security/security.c
> index 3180a6f30625..82e29c477fa4 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -46,7 +46,9 @@ 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;
> +static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init = {
> + .lbs_task = sizeof(int), /* slot number for the "display" LSM */
> +};
>
> /* Boot-time LSM user choice */
> static __initdata const char *chosen_lsm_order;
> @@ -423,8 +425,10 @@ 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;
> +static struct lsm_id *lsm_slotlist[LSMBLOB_ENTRIES];
>
> /**
> * security_add_hooks - Add a modules hooks to the hook lists.
> @@ -444,6 +448,7 @@ 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 +569,8 @@ 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 +579,15 @@ 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 +1579,24 @@ 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;
> + }
> +
> + ndisplay = task->security;
> + if (ndisplay && odisplay)
> + *ndisplay = *odisplay;
> +
> + return 0;
> }
>
> void security_task_free(struct task_struct *task)
> @@ -1967,10 +1993,29 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
> char **value)
> {
> struct security_hook_list *hp;
> + int *display = current->security;
> + 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 +2025,46 @@ 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")) {
> + /*
> + * 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 +2084,15 @@ 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 = current->security;
>
> 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 +2102,15 @@ int security_secctx_to_secid(const char *secdata, u32 seclen,
> struct lsmblob *blob)
> {
> struct security_hook_list *hp;
> - int rc;
> + int *display = current->security;
>
> 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 +2118,15 @@ 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 == LSMBLOB_INVALID ||
> + *display == hp->lsmid->slot) {
> + hp->hook.release_secctx(secdata, seclen);
> + return;
> + }
> }
> EXPORT_SYMBOL(security_release_secctx);
>
> @@ -2163,8 +2251,15 @@ 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 = current->security;
> + 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,
>
