Commit 54708d28 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

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: default avatar"Jin, Yihua" <>
Signed-off-by: default avatarOleg Nesterov <>
Cc: "Eric W. Biederman" <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 3a49f3d2
......@@ -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;
p = pid_task(proc_pid(inode), PIDTYPE_PID);
if (p && same_thread_group(p, current))
rv = 0;
return rv;
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