[PATCH AUTOSEL 5.4 13/23] proc: don't allow async path resolution of /proc/self components

From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>, Sasha Levin <sashal@kernel.org>,
	linux-fsdevel@vger.kernel.org
Subject: [PATCH AUTOSEL 5.4 13/23] proc: don't allow async path resolution of /proc/self components
Date: Wed, 25 Nov 2020 10:36:28 -0500	[thread overview]
Message-ID: <20201125153638.810419-13-sashal@kernel.org> (raw)
In-Reply-To: <20201125153638.810419-1-sashal@kernel.org>

From: Jens Axboe <axboe@kernel.dk>

[ 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>
---
 fs/proc/self.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/proc/self.c b/fs/proc/self.c
index 32af065397f80..582336862d258 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -16,6 +16,13 @@ static const char *proc_self_get_link(struct dentry *dentry,
 	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);
 	/* max length of unsigned int in decimal + NULL term */
-- 
2.27.0

