From: Paul Moore paul@paul-moore.com
commit 35a196bef449b5824033865b963ed9a43fb8c730 upstream.
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: stable@vger.kernel.org Reported-by: "chengjian (D)" cj.chengjian@huawei.com Signed-off-by: Paul Moore paul@paul-moore.com Acked-by: John Johansen john.johansen@canonical.com Acked-by: James Morris james.morris@microsoft.com Acked-by: Casey Schaufler casey@schaufler-ca.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/proc/base.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2542,6 +2542,11 @@ static ssize_t proc_pid_attr_write(struc 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)