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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 21/57] proc: dont allow async path resolution of /proc/self components
Date:   Tue,  1 Dec 2020 09:53:26 +0100
Message-Id: <20201201084650.205087954@linuxfoundation.org>
In-Reply-To: <20201201084647.751612010@linuxfoundation.org>
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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 cc6d4253399d1..7922edf70ce1a 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