linux-kernel - [PATCH 4.19 03/84] HID: hidraw, uhid: Always report EPOLLOUT

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Message-Id: <20200116231713.677596697@linuxfoundation.org>
Date:   Fri, 17 Jan 2020 00:17:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Kosina <jkosina@...e.cz>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 03/84] HID: hidraw, uhid: Always report EPOLLOUT

From: Jiri Kosina <jkosina@...e.cz>

[ Upstream commit 9e635c2851df6caee651e589fbf937b637973c91 ]

hidraw and uhid device nodes are always available for writing so we should
always report EPOLLOUT and EPOLLWRNORM bits, not only in the cases when
there is nothing to read.

Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Fixes: be54e7461ffdc ("HID: uhid: Fix returning EPOLLOUT from uhid_char_poll")
Fixes: 9f3b61dc1dd7b ("HID: hidraw: Fix returning EPOLLOUT from hidraw_poll")
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hid/hidraw.c | 7 ++++---
 drivers/hid/uhid.c   | 5 +++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index a025b6961896..c4ba2d28dd73 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -257,13 +257,14 @@ out:
 static __poll_t hidraw_poll(struct file *file, poll_table *wait)
 {
 	struct hidraw_list *list = file->private_data;
+	__poll_t mask = EPOLLOUT | EPOLLWRNORM; /* hidraw is always writable */
 
 	poll_wait(file, &list->hidraw->wait, wait);
 	if (list->head != list->tail)
-		return EPOLLIN | EPOLLRDNORM;
+		mask |= EPOLLIN | EPOLLRDNORM;
 	if (!list->hidraw->exist)
-		return EPOLLERR | EPOLLHUP;
-	return EPOLLOUT | EPOLLWRNORM;
+		mask |= EPOLLERR | EPOLLHUP;
+	return mask;
 }
 
 static int hidraw_open(struct inode *inode, struct file *file)
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 8508dbac2657..29e63330c1b5 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -769,13 +769,14 @@ unlock:
 static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
 {
 	struct uhid_device *uhid = file->private_data;
+	__poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
 
 	poll_wait(file, &uhid->waitq, wait);
 
 	if (uhid->head != uhid->tail)
-		return EPOLLIN | EPOLLRDNORM;
+		mask |= EPOLLIN | EPOLLRDNORM;
 
-	return EPOLLOUT | EPOLLWRNORM;
+	return mask;
 }
 
 static const struct file_operations uhid_fops = {
-- 
2.20.1