From 35a196bef449b5824033865b963ed9a43fb8c730 Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Fri, 19 Apr 2019 14:55:12 -0400 Subject: proc: prevent changes to overridden credentials Prevent userspace from changing the the /proc/PID/attr values if the task's credentials are currently overriden. This not only makes sense conceptually, it also prevents some really bizarre error cases caused when trying to commit credentials to a task with overridden credentials. Cc: Reported-by: "chengjian (D)" Signed-off-by: Paul Moore Acked-by: John Johansen Acked-by: James Morris Acked-by: Casey Schaufler --- fs/proc/base.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'fs/proc/base.c') diff --git a/fs/proc/base.c b/fs/proc/base.c index ddef482f1334..87ba007b86db 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2539,6 +2539,11 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf, rcu_read_unlock(); return -EACCES; } + /* Prevent changes to overridden credentials. */ + if (current_cred() != current_real_cred()) { + rcu_read_unlock(); + return -EBUSY; + } rcu_read_unlock(); if (count > PAGE_SIZE) -- cgit v1.2.3-59-g8ed1b