From 21f6e33e333e7d143c9a02574a66b55e312c491a Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Tue, 23 Apr 2019 15:42:48 +0800 Subject: [PATCH] proc: prevent changes to overridden credentials hulk inclusion category: bugfix bugzilla: 13668 CVE: NA ------------------------------------------------- Prevent userspace from changing the the /proc/PID/attr values if the task's credentials are currently overridden. 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: James Morris Acked-by: John Johansen Acked-by: Casey Schaufler Signed-off-by: Yang Yingliang Reviewed-by: Cheng Jian Signed-off-by: Yang Yingliang --- fs/proc/base.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index 81d77b15b347..f999e8bd3771 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2542,6 +2542,11 @@ 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) -- GitLab