From: Jens Axboe <axboe@kernel.dk>
Date: Fri, 13 Nov 2020 23:47:52 +0000 (-0700)
Subject: proc: don't allow async path resolution of /proc/self components
X-Git-Tag: v4.4.247~17
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ebb83fd9dbd29d844c553d28565b5f86e47790e0;p=thirdparty%2Fkernel%2Fstable.git

proc: don't allow async path resolution of /proc/self components

[ Upstream commit 8d4c3e76e3be11a64df95ddee52e99092d42fc19 ]

If this is attempted by a kthread, then return -EOPNOTSUPP as we don't
currently support that. Once we can get task_pid_ptr() doing the right
thing, then this can go away again.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/fs/proc/self.c b/fs/proc/self.c
index 2dcc2558b3aa7..dffbe533d53fc 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -24,6 +24,13 @@ static const char *proc_self_follow_link(struct dentry *dentry, void **cookie)
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char *name;
 
+	/*
+	 * Not currently supported. Once we can inherit all of struct pid,
+	 * we can allow this.
+	 */
+	if (current->flags & PF_KTHREAD)
+		return ERR_PTR(-EOPNOTSUPP);
+
 	if (!tgid)
 		return ERR_PTR(-ENOENT);
 	/* 11 for max length of signed int in decimal + NULL term */