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authorPaul Moore <paul@paul-moore.com>2019-04-19 14:55:12 -0400
committerPaul Moore <paul@paul-moore.com>2019-04-29 09:51:21 -0400
commit35a196bef449b5824033865b963ed9a43fb8c730 (patch)
treebed797d4bac8508de8e185e3bd08247a9ed33891
parentc750e6929d3c76d13d1d0ba475989d6dd74785d5 (diff)
downloadlinux-35a196bef449b5824033865b963ed9a43fb8c730.tar.bz2
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: <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>
-rw-r--r--fs/proc/base.c5
1 files changed, 5 insertions, 0 deletions
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)