linux-kernel - [PATCH] autofs: clear O

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Message-ID: <871s4fi5b5.fsf@notabene.neil.brown.name>
Date:   Mon, 11 Feb 2019 10:37:02 +1100
From:   NeilBrown <neilb@...e.com>
To:     Ian Kent <raven@...maw.net>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     autofs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] autofs: clear O_NONBLOCK on the pipe.


autofs does not expect the pipe it is given
to have O_NONBLOCK set - specifically if __kernel_write()
in autofs_write() returns -EAGAIN, this is treated
as a fatal error and the pipe is closed.

For safety autofs should, therefore, clear the O_NONBLOCK flag.

Releases of systemd prior to 8th February 2019 used
  pipe2(p, O_NONBLOCK|O_CLOEXEC)
and thus (inadvertently) set this flag.

Signed-off-by: NeilBrown <neilb@...e.com>
---
 fs/autofs/autofs_i.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/autofs/autofs_i.h b/fs/autofs/autofs_i.h
index 3e59f0ed777b..331192bed0d5 100644
--- a/fs/autofs/autofs_i.h
+++ b/fs/autofs/autofs_i.h
@@ -215,6 +215,8 @@ static inline int autofs_prepare_pipe(struct file *pipe)
 		return -EINVAL;
 	/* We want a packet pipe */
 	pipe->f_flags |= O_DIRECT;
+	/* We don't expect -EAGAIN */
+	pipe->f_flags &= ~O_NONBLOCK;
 	return 0;
 }
 
-- 
2.14.0.rc0.dirty


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