From: Paul Moore <paul@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Reported-by: "chengjian (D)" <cj.chengjian@xxxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Acked-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
Acked-by: James Morris <james.morris@xxxxxxxxxxxxx>
Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2540,6 +2540,11 @@ 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)
