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UPSTREAM: proc: actually make proc_fd_permission() thread-friendly

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(cherry pick from commit 54708d2858e79a2bdda10bf8a20c80eb96c20613)

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/<tid>/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" <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>
Bug: 26016905
Change-Id: I1894c78d0b13f0bde8cde84bd142ba67590dc0f1
This commit is contained in:
Oleg Nesterov 2015-11-06 16:30:06 -08:00 committed by Swetha Chikkaboraiah
parent 1616e43a78
commit 5b82e8b497
1 changed files with 11 additions and 3 deletions
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14
fs/proc/fd.c
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@ -302,11 +302,19 @@ 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;
}