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);
_
--
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