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proc,security: move restriction on writing /proc/pid/attr nodes to proc

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Processes can only alter their own security attributes via
/proc/pid/attr nodes.  This is presently enforced by each individual
security module and is also imposed by the Linux credentials
implementation, which only allows a task to alter its own credentials.
Move the check enforcing this restriction from the individual
security modules to proc_pid_attr_write() before calling the security hook,
and drop the unnecessary task argument to the security hook since it can
only ever be the current task.

Signed-off-by: Stephen Smalley <[email protected]>
Acked-by: Casey Schaufler <[email protected]>
Acked-by: John Johansen <[email protected]>
Signed-off-by: Paul Moore <[email protected]>
This commit is contained in:
Stephen Smalley 2017-01-09 10:07:31 -05:00 • committed by Paul Moore
commit b21507e272
7 changed files with 18 additions and 37 deletions
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13
fs/proc/base.c
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@ -2488,6 +2488,12 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
length = -ESRCH;
if (!task)
goto out_no_task;
/* A task may only write its own attributes. */
length = -EACCES;
if (current != task)
goto out;
if (count > PAGE_SIZE)
count = PAGE_SIZE;
@ -2503,14 +2509,13 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
}
/* Guard against adverse ptrace interaction */
length = mutex_lock_interruptible(&task->signal->cred_guard_mutex);
length = mutex_lock_interruptible(&current->signal->cred_guard_mutex);
if (length < 0)
goto out_free;
length = security_setprocattr(task,
(char*)file->f_path.dentry->d_name.name,
length = security_setprocattr(file->f_path.dentry->d_name.name,
page, count);
mutex_unlock(&task->signal->cred_guard_mutex);
mutex_unlock(&current->signal->cred_guard_mutex);
out_free:
kfree(page);
out: