linux-kernel - [PATCH 5.10 14/97] gfs2: Disable page faults during lockless buffered reads

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220523165814.598631250@linuxfoundation.org>
Date:   Mon, 23 May 2022 19:05:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andreas Gruenbacher <agruenba@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 14/97] gfs2: Disable page faults during lockless buffered reads

From: Andreas Gruenbacher <agruenba@...hat.com>

[ Upstream commit 52f3f033a5dbd023307520af1ff551cadfd7f037 ]

During lockless buffered reads, filemap_read() holds page cache page
references while trying to copy data to the user-space buffer.  The
calling process isn't holding the inode glock, but the page references
it holds prevent those pages from being removed from the page cache, and
that prevents the underlying inode glock from being moved to another
node.  Thus, we can end up in the same kinds of distributed deadlock
situations as with normal (non-lockless) buffered reads.

Fix that by disabling page faults during lockless reads as well.

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/gfs2/file.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 2e6f622ed428..55a8eb3c1963 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -858,14 +858,16 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			return ret;
 		iocb->ki_flags &= ~IOCB_DIRECT;
 	}
+	pagefault_disable();
 	iocb->ki_flags |= IOCB_NOIO;
 	ret = generic_file_read_iter(iocb, to);
 	iocb->ki_flags &= ~IOCB_NOIO;
+	pagefault_enable();
 	if (ret >= 0) {
 		if (!iov_iter_count(to))
 			return ret;
 		written = ret;
-	} else {
+	} else if (ret != -EFAULT) {
 		if (ret != -EAGAIN)
 			return ret;
 		if (iocb->ki_flags & IOCB_NOWAIT)
-- 
2.35.1