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Date: Mon, 26 Aug 2013 19:29:27 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Kees Cook <keescook@...omium.org>
CC: LKLM <linux-kernel@...r.kernel.org>,
LSM <linux-security-module@...r.kernel.org>,
SE Linux <selinux@...ho.nsa.gov>,
James Morris <jmorris@...ei.org>,
John Johansen <john.johansen@...onical.com>,
Eric Paris <eparis@...hat.com>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v14 0/6] LSM: Multiple concurrent LSMs
On 8/6/2013 3:36 PM, Kees Cook wrote:
> On Tue, Aug 6, 2013 at 3:25 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
>> On 8/5/2013 11:30 PM, Kees Cook wrote:
>>> On Thu, Jul 25, 2013 at 11:52 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
>>>> The /proc/*/attr interfaces are given to one LSM. This can be
>>>> done by setting CONFIG_SECURITY_PRESENT. Additional interfaces
>>>> have been created in /proc/*/attr so that each LSM has its own
>>>> named interfaces. The name of the presenting LSM can be read from
>>> For me, this is one problem that was bothering me, but it was a cosmetic
>>> one that I'd mentioned before: I really disliked the /proc/$pid/attr
>>> interface being named "$lsm.$file". I feel it's important to build
>>> directories in attr/ for each LSM. So, I spent time to figure out a way to
>>> do this. This patch changes the interface to /proc/$pid/attr/$lsm/$file
>>> instead, which I feel has a much more appealing organizational structure.
>> I will confess that the reason I went with <lsm>.current instead of
>> <lsm>/current was that the former was easier to implement.
> Yeah, that's totally fine. It wasn't very obvious (to me) how to
> implement this initially, so no problem at all. I'm glad there was
> something more than bug fixes I could contribute to this series. :)
Oh dear. I'm rebasing for 3.12 and the macros don't generate compiling
code any longer. It seems that, among other things, readdir is no longer
a member of file_operations.
>
>>> -Kees
>>>
>>> ---
>>> Subject: [PATCH] LSM: use subdirectories for LSM attr files
>>>
>>> Instead of filling the /proc/$pid/attr/ directory with every LSM's needed
>>> attr files, insert a directory entry for each LSM which contains the
>>> needed files.
>>>
>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>> ---
>>> fs/proc/base.c | 95 ++++++++++++++++++++++++++++++++++++----------
>>> fs/proc/internal.h | 1 +
>>> include/linux/security.h | 11 +++---
>>> security/security.c | 67 ++++++++++++++------------------
>>> 4 files changed, 112 insertions(+), 62 deletions(-)
>>>
>>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>>> index 941fe83..4c80ffd 100644
>>> --- a/fs/proc/base.c
>>> +++ b/fs/proc/base.c
>>> @@ -138,6 +138,10 @@ struct pid_entry {
>>> NOD(NAME, (S_IFREG|(MODE)), \
>>> NULL, &proc_single_file_operations, \
>>> { .proc_show = show } )
>>> +#define ATTR(LSM, NAME, MODE) \
>>> + NOD(NAME, (S_IFREG|(MODE)), \
>>> + NULL, &proc_pid_attr_operations, \
>>> + { .lsm = LSM } )
>>>
>>> /*
>>> * Count the number of hardlinks for the pid_entry table, excluding the .
>>> @@ -2292,7 +2296,7 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
>>> if (!task)
>>> return -ESRCH;
>>>
>>> - length = security_getprocattr(task,
>>> + length = security_getprocattr(task, PROC_I(inode)->op.lsm,
>>> (char*)file->f_path.dentry->d_name.name,
>>> &p);
>>> put_task_struct(task);
>>> @@ -2335,7 +2339,7 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
>>> if (length < 0)
>>> goto out_free;
>>>
>>> - length = security_setprocattr(task,
>>> + length = security_setprocattr(task, PROC_I(inode)->op.lsm,
>>> (char*)file->f_path.dentry->d_name.name,
>>> (void*)page, count);
>>> mutex_unlock(&task->signal->cred_guard_mutex);
>>> @@ -2353,29 +2357,82 @@ static const struct file_operations proc_pid_attr_operations = {
>>> .llseek = generic_file_llseek,
>>> };
>>>
>>> +#define LSM_DIR_OPS(LSM) \
>>> +static int proc_##LSM##_attr_dir_readdir(struct file * filp, \
>>> + void * dirent, filldir_t filldir) \
>>> +{ \
>>> + return proc_pident_readdir(filp, dirent, filldir, \
>>> + LSM##_attr_dir_stuff, \
>>> + ARRAY_SIZE(LSM##_attr_dir_stuff)); \
>>> +} \
>>> +\
>>> +static const struct file_operations proc_##LSM##_attr_dir_ops = { \
>>> + .read = generic_read_dir, \
>>> + .readdir = proc_##LSM##_attr_dir_readdir, \
>>> + .llseek = default_llseek, \
>>> +}; \
>>> +\
>>> +static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \
>>> + struct dentry *dentry, unsigned int flags) \
>>> +{ \
>>> + return proc_pident_lookup(dir, dentry, \
>>> + LSM##_attr_dir_stuff, \
>>> + ARRAY_SIZE(LSM##_attr_dir_stuff)); \
>>> +} \
>>> +\
>>> +static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
>>> + .lookup = proc_##LSM##_attr_dir_lookup, \
>>> + .getattr = pid_getattr, \
>>> + .setattr = proc_setattr, \
>>> +};
>> That's one hell of a macro you got there, Kees.
>> I'm not saying it's bad, but it is quite the mouthful.
> Heh, yeah. And this is the reduced version! I haven't found a good way
> to make this smaller yet.
>
>>> +
>>> +#ifdef CONFIG_SECURITY_SELINUX
>>> +static const struct pid_entry selinux_attr_dir_stuff[] = {
>>> + ATTR("selinux", "current", S_IRUGO|S_IWUGO),
>>> + ATTR("selinux", "prev", S_IRUGO),
>>> + ATTR("selinux", "exec", S_IRUGO|S_IWUGO),
>>> + ATTR("selinux", "fscreate", S_IRUGO|S_IWUGO),
>>> + ATTR("selinux", "keycreate", S_IRUGO|S_IWUGO),
>>> + ATTR("selinux", "sockcreate", S_IRUGO|S_IWUGO),
>>> +};
>>> +LSM_DIR_OPS(selinux);
>>> +#endif
>>> +
>>> +#ifdef CONFIG_SECURITY_SMACK
>>> +static const struct pid_entry smack_attr_dir_stuff[] = {
>>> + ATTR("smack", "current", S_IRUGO|S_IWUGO),
>>> +};
>>> +LSM_DIR_OPS(smack);
>>> +#endif
>>> +
>>> +#ifdef CONFIG_SECURITY_APPARMOR
>>> +static const struct pid_entry apparmor_attr_dir_stuff[] = {
>>> + ATTR("apparmor", "current", S_IRUGO|S_IWUGO),
>>> + ATTR("apparmor", "prev", S_IRUGO),
>>> + ATTR("apparmor", "exec", S_IRUGO|S_IWUGO),
>>> +};
>>> +LSM_DIR_OPS(apparmor);
>>> +#endif
>>> +
>> %s/dir_stuff/dir_entries/g
>> It doesn't have to be "entries", but "stuff" is horribly non-descriptive.
> Using "entries" is fine by me. I was modeling it entirely after the
> existing code (see "attr_dir_stuff" below).
>
>>
>>> static const struct pid_entry attr_dir_stuff[] = {
>>> - REG("current", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("prev", S_IRUGO, proc_pid_attr_operations),
>>> - REG("exec", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("fscreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("keycreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("context", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> + ATTR(NULL, "current", S_IRUGO|S_IWUGO),
>>> + ATTR(NULL, "prev", S_IRUGO),
>>> + ATTR(NULL, "exec", S_IRUGO|S_IWUGO),
>>> + ATTR(NULL, "fscreate", S_IRUGO|S_IWUGO),
>>> + ATTR(NULL, "keycreate", S_IRUGO|S_IWUGO),
>>> + ATTR(NULL, "sockcreate", S_IRUGO|S_IWUGO),
>>> + ATTR(NULL, "context", S_IRUGO|S_IWUGO),
>>> #ifdef CONFIG_SECURITY_SELINUX
>>> - REG("selinux.current", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("selinux.prev", S_IRUGO, proc_pid_attr_operations),
>>> - REG("selinux.exec", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("selinux.fscreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("selinux.keycreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("selinux.sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> + DIR("selinux", S_IRUGO|S_IXUGO,
>>> + proc_selinux_attr_dir_inode_ops, proc_selinux_attr_dir_ops),
>>> #endif
>>> #ifdef CONFIG_SECURITY_SMACK
>>> - REG("smack.current", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> + DIR("smack", S_IRUGO|S_IXUGO,
>>> + proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
>>> #endif
>>> #ifdef CONFIG_SECURITY_APPARMOR
>>> - REG("apparmor.current", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> - REG("apparmor.prev", S_IRUGO, proc_pid_attr_operations),
>>> - REG("apparmor.exec", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
>>> + DIR("apparmor", S_IRUGO|S_IXUGO,
>>> + proc_apparmor_attr_dir_inode_ops, proc_apparmor_attr_dir_ops),
>>> #endif
>>>
>>> };
>>> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
>>> index d600fb0..795f649 100644
>>> --- a/fs/proc/internal.h
>>> +++ b/fs/proc/internal.h
>>> @@ -56,6 +56,7 @@ union proc_op {
>>> int (*proc_show)(struct seq_file *m,
>>> struct pid_namespace *ns, struct pid *pid,
>>> struct task_struct *task);
>>> + const char *lsm;
>>> };
>>>
>>> struct proc_inode {
>>> diff --git a/include/linux/security.h b/include/linux/security.h
>>> index d60e21c..fa89618 100644
>>> --- a/include/linux/security.h
>>> +++ b/include/linux/security.h
>>> @@ -2115,9 +2115,10 @@ int security_sem_semctl(struct sem_array *sma, int cmd);
>>> int security_sem_semop(struct sem_array *sma, struct sembuf *sops,
>>> unsigned nsops, int alter);
>>> void security_d_instantiate(struct dentry *dentry, struct inode *inode);
>>> -int security_getprocattr(struct task_struct *p, char *name, char **value);
>>> -int security_setprocattr(struct task_struct *p, char *name, void *value,
>>> - size_t size);
>>> +int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>>> + char **value);
>>> +int security_setprocattr(struct task_struct *p, const char *lsm, char *name,
>>> + void *value, size_t size);
>>> int security_netlink_send(struct sock *sk, struct sk_buff *skb);
>>> int security_secid_to_secctx(struct secids *secid, char **secdata, u32 *seclen,
>>> struct security_operations **secops);
>>> @@ -2801,8 +2802,8 @@ static inline void security_d_instantiate(struct dentry *dentry,
>>> struct inode *inode)
>>> { }
>>>
>>> -static inline int security_getprocattr(struct task_struct *p, char *name,
>>> - char **value)
>>> +static inline int security_getprocattr(struct task_struct *p, char *lsm,
>>> + char *name, char **value)
>>> {
>>> return -EINVAL;
>>> }
>>> diff --git a/security/security.c b/security/security.c
>>> index 119a377..499af30 100644
>>> --- a/security/security.c
>>> +++ b/security/security.c
>>> @@ -1897,74 +1897,65 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
>>> }
>>> EXPORT_SYMBOL(security_d_instantiate);
>>>
>>> -int security_getprocattr(struct task_struct *p, char *name, char **value)
>>> +int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>>> + char **value)
>>> {
>>> struct security_operations *sop = NULL;
>>> struct secids secid;
>>> - char *lsm;
>>> - int lsmlen;
>>> int ret;
>>>
>>> /*
>>> - * Names will either be in the legacy form containing
>>> - * no periods (".") or they will be the LSM name followed
>>> - * by the legacy suffix. "current" or "selinux.current"
>>> - * The exception is "context", which gets all of the LSMs.
>>> - *
>>> - * Legacy names are handled by the presenting LSM.
>>> - * Suffixed names are handled by the named LSM.
>>> + * Target LSM will be either NULL or looked up by name. Names with
>>> + * a NULL LSM (legacy) are handled by the presenting LSM. The
>>> + * exception is "context", which gets all of the LSMs.
>>> */
>>> if (strcmp(name, "context") == 0) {
>>> + char *lsmname;
>>> + int lsmlen;
>>> +
>>> security_task_getsecid(p, &secid);
>>> - ret = security_secid_to_secctx(&secid, &lsm, &lsmlen, &sop);
>>> + ret = security_secid_to_secctx(&secid, &lsmname, &lsmlen, &sop);
>>> if (ret == 0) {
>>> - *value = kstrdup(lsm, GFP_KERNEL);
>>> + *value = kstrdup(lsmname, GFP_KERNEL);
>>> if (*value == NULL)
>>> ret = -ENOMEM;
>>> else
>>> ret = strlen(*value);
>>> - security_release_secctx(lsm, lsmlen, sop);
>>> + security_release_secctx(lsmname, lsmlen, sop);
>>> }
>>> return ret;
>>> }
>>>
>>> - if (present_ops && !strchr(name, '.'))
>>> - return present_getprocattr(p, name, value);
>>> -
>>> - for_each_hook(sop, getprocattr) {
>>> - lsm = sop->name;
>>> - lsmlen = strlen(lsm);
>>> - if (!strncmp(name, lsm, lsmlen) && name[lsmlen] == '.')
>>> - return sop->getprocattr(p, name + lsmlen + 1, value);
>>> + if (!lsm) {
>>> + if (present_ops)
>>> + return present_getprocattr(p, name, value);
>>> + } else {
>>> + for_each_hook(sop, getprocattr) {
>>> + if (!strcmp(lsm, sop->name))
>>> + return sop->getprocattr(p, name, value);
>>> + }
>>> }
>>> return -EINVAL;
>>> }
>>>
>>> -int security_setprocattr(struct task_struct *p, char *name, void *value,
>>> - size_t size)
>>> +int security_setprocattr(struct task_struct *p, const char *lsm, char *name,
>>> + void *value, size_t size)
>>> {
>>> struct security_operations *sop;
>>> - char *lsm;
>>> - int lsmlen;
>>>
>>> /*
>>> - * Names will either be in the legacy form containing
>>> - * no periods (".") or they will be the LSM name followed
>>> - * by the legacy suffix.
>>> - * "current" or "selinux.current"
>>> - *
>>> - * Legacy names are handled by the presenting LSM.
>>> - * Suffixed names are handled by the named LSM.
>>> + * Target LSM will be either NULL or looked up by name. Names with
>>> + * a NULL LSM (legacy) are handled by the presenting LSM. The
>>> */
>>> if (present_ops && !strchr(name, '.'))
>>> return present_setprocattr(p, name, value, size);
>> We'll want to loose the preceding two lines, and add some later.
>>
>>
>>> - for_each_hook(sop, setprocattr) {
>>> - lsm = sop->name;
>>> - lsmlen = strlen(lsm);
>>> - if (!strncmp(name, lsm, lsmlen) && name[lsmlen] == '.')
>>> - return sop->setprocattr(p, name + lsmlen + 1, value,
>>> - size);
>>> + if (lsm) {
>>> + for_each_hook(sop, setprocattr) {
>>> + if (!strcmp(lsm, sop->name))
>>> + return sop->setprocattr(p, name, value,
>>> + size);
>>> + }
>>> - }
>> + } else if (present_ops)
>> + return present_setprocattr(p, name, value, size);
> Ah yes, this is better. Great!
>
> -Kees
>
>>> return -EINVAL;
>>> }
--
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