From 54708d2858e79a2bdda10bf8a20c80eb96c20613 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 6 Nov 2015 16:30:06 -0800 Subject: [PATCH] proc: actually make proc_fd_permission() thread-friendly The commit 96d0df79f264 ("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//fd/ or /proc/thread-self/fd if generic_permission() fails. Change proc_fd_permission() to check same_thread_group(pid_task(), current). Fixes: 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly") Reported-by: "Jin, Yihua" Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/fd.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 6e5fcd00733e..3c2a915c695a 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -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; } -- 2.20.1