linux-kernel - [PATCH AUTOSEL 4.4 5/8] proc: don't allow async path resolution of /proc/self components

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Message-Id: <20201125153808.811104-5-sashal@kernel.org>
Date:   Wed, 25 Nov 2020 10:38:05 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 5/8] proc: don't allow async path resolution of /proc/self components

From: Jens Axboe <axboe@...nel.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@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/proc/self.c | 7 +++++++
 1 file changed, 7 insertions(+)

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 */
-- 
2.27.0