From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: 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 <adobriyan@xxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/base.c | 6 ++++++ 1 file changed, 6 insertions(+) diff -puN fs/proc/base.c~proc-revalidate-kernel-thread-inodes-to-root-root fs/proc/base.c --- a/fs/proc/base.c~proc-revalidate-kernel-thread-inodes-to-root-root +++ a/fs/proc/base.c @@ -1693,6 +1693,12 @@ void task_dump_owner(struct task_struct 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); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html