Commit 54708d28 authored Nov 06, 2015 by Oleg Nesterov Committed by Linus Torvalds Nov 06, 2015

proc: actually make proc_fd_permission() thread-friendly



The commit 96d0df79 ("proc: make proc_fd_permission() thread-friendly")
fixed the access to /proc/self/fd from sub-threads, but introduced another
problem: a sub-thread can't access /proc/<tid>/fd/ or /proc/thread-self/fd
if generic_permission() fails.

Change proc_fd_permission() to check same_thread_group(pid_task(), current).

Fixes: 96d0df79 ("proc: make proc_fd_permission() thread-friendly")
Reported-by: "Jin, Yihua" <yihua.jin@intel.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 3a49f3d2

fs/proc/fd.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -291,11 +291,19 @@ static struct dentry proc_lookupfd(struct inode dir, struct dentry *dentry,
		*/
		int proc_fd_permission(struct inode *inode, int mask)
		{
		int rv = generic_permission(inode, mask);
		struct task_struct *p;
		int rv;

		rv = generic_permission(inode, mask);
		if (rv == 0)
		return 0;
		if (task_tgid(current) == proc_pid(inode))
		return rv;

		rcu_read_lock();
		p = pid_task(proc_pid(inode), PIDTYPE_PID);
		if (p && same_thread_group(p, current))
		rv = 0;
		rcu_read_unlock();

		return rv;
		}

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