1 files changed, 14 insertions, 0 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ccf86f16d9f0..7e9f07bf260d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -407,6 +407,20 @@ static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
         unsigned long *entries;
         int err;
 
+        /*
+         * The ability to racily run the kernel stack unwinder on a running task
+         * and then observe the unwinder output is scary; while it is useful for
+         * debugging kernel issues, it can also allow an attacker to leak kernel
+         * stack contents.
+         * Doing this in a manner that is at least safe from races would require
+         * some work to ensure that the remote task can not be scheduled; and
+         * even then, this would still expose the unwinder as local attack
+         * surface.
+         * Therefore, this interface is restricted to root.
+         */
+        if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
+                return -EACCES;
+
         entries = kmalloc_array(MAX_STACK_TRACE_DEPTH, sizeof(*entries),
                                 GFP_KERNEL);
         if (!entries)