From 2e0ad552f5f8cd0fda02bc45fcd2b89821c62fd1 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Fri, 20 Apr 2018 14:56:03 -0700 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. Link: http://lkml.kernel.org/r/20180412220109.GA20978@avx2 Signed-off-by: Alexey Dobriyan Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index eafa39a..1b2ede6 100644 --- 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); -- 2.7.4