releases/5.10.4/proc-mountinfo-make-splice-available-again.patch

From aa543f188e7b8e73693381cb57737ee01fc67bc6 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Sun, 27 Dec 2020 10:56:33 -0800
Subject: proc mountinfo: make splice available again
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From: Linus Torvalds <torvalds@linux-foundation.org>

[ Upstream commit 14e3e989f6a5d9646b6cf60690499cc8bdc11f7d ]

Since commit 36e2c7421f02 ("fs: don't allow splice read/write without
explicit ops") we've required that file operation structures explicitly
enable splice support, rather than falling back to the default handlers.

Most /proc files use the indirect 'struct proc_ops' to describe their
file operations, and were fixed up to support splice earlier in commits
40be821d627c..b24c30c67863, but the mountinfo files interact with the
VFS directly using their own 'struct file_operations' and got missed as
a result.

This adds the necessary support for splice to work for /proc/*/mountinfo
and friends.

Reported-by: Joan Bruguera Micó <joanbrugueram@gmail.com>
Reported-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209971
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/proc_namespace.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -320,7 +320,8 @@ static int mountstats_open(struct inode
 
 const struct file_operations proc_mounts_operations = {
 	.open		= mounts_open,
-	.read		= seq_read,
+	.read_iter	= seq_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 	.poll		= mounts_poll,
@@ -328,7 +329,8 @@ const struct file_operations proc_mounts
 
 const struct file_operations proc_mountinfo_operations = {
 	.open		= mountinfo_open,
-	.read		= seq_read,
+	.read_iter	= seq_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 	.poll		= mounts_poll,
@@ -336,7 +338,8 @@ const struct file_operations proc_mounti
 
 const struct file_operations proc_mountstats_operations = {
 	.open		= mountstats_open,
-	.read		= seq_read,
+	.read_iter	= seq_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 };