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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id q3sm182044pgv.21.2019.06.26.16.12.34 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 26 Jun 2019 16:12:34 -0700 (PDT) Date: Wed, 26 Jun 2019 16:12:33 -0700 From: Kees Cook To: Casey Schaufler Cc: casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com, sds@tycho.nsa.gov Subject: Re: [PATCH v4 15/23] LSM: Specify which LSM to display Message-ID: <201906261612.49AEC4F9CE@keescook> References: <20190626192234.11725-1-casey@schaufler-ca.com> <20190626192234.11725-16-casey@schaufler-ca.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190626192234.11725-16-casey@schaufler-ca.com> Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org On Wed, Jun 26, 2019 at 12:22:26PM -0700, 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 Reviewed-by: Kees Cook -Kees > --- > 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, > -- > 2.20.1 > -- Kees Cook