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Subject[PATCH] proc: revalidate kernel thread inodes to root:root
task_dump_owner() has the following code:

mm = task->mm;
if (mm) {
if (get_dumpable(mm) != SUID_DUMP_USER) {
uid = ...
}
}

Check for ->mm is buggy -- kernel thread might be borrowing mm
and inode will go to some random uid:gid pair.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

fs/proc/base.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1693,6 +1693,12 @@ void task_dump_owner(struct task_struct *task, umode_t mode,
kuid_t uid;
kgid_t gid;

+ if (unlikely(task->flags & PF_KTHREAD)) {
+ *ruid = GLOBAL_ROOT_UID;
+ *rgid = GLOBAL_ROOT_GID;
+ return;
+ }
+
/* Default to the tasks effective ownership */
rcu_read_lock();
cred = __task_cred(task);
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