linux-kernel - [PATCH v2 1/3] fanotify: Ensure consistent variable type for response

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Date:   Thu, 28 Apr 2022 20:44:34 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org
Cc:     Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Richard Guy Briggs <rgb@...hat.com>, Jan Kara <jack@...e.cz>
Subject: [PATCH v2 1/3] fanotify: Ensure consistent variable type for response

The user space API for the response variable is __u32. This patch makes
sure that the whole path through the kernel uses __u32 so that there is
no sign extension or truncation of the user space response.

Suggested-by: Steve Grubb <sgrubb@...hat.com>
Link: https://lore.kernel.org/r/12617626.uLZWGnKmhe@x2
Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
Link: https://lore.kernel.org/r/aa98a3ad00666a6fc0ce411755de4a1a60f5c0cd.1651174324.git.rgb@redhat.com
---
 fs/notify/fanotify/fanotify.h      | 2 +-
 fs/notify/fanotify/fanotify_user.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index a3d5b751cac5..70acfd497771 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -425,7 +425,7 @@ FANOTIFY_PE(struct fanotify_event *event)
 struct fanotify_perm_event {
 	struct fanotify_event fae;
 	struct path path;
-	unsigned short response;	/* userspace answer to the event */
+	__u32 response;			/* userspace answer to the event */
 	unsigned short state;		/* state of the event */
 	int fd;		/* fd we passed to userspace for this event */
 };
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 9b32b76a9c30..694516470660 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -289,7 +289,7 @@ static int create_fd(struct fsnotify_group *group, struct path *path,
  */
 static void finish_permission_event(struct fsnotify_group *group,
 				    struct fanotify_perm_event *event,
-				    unsigned int response)
+				    __u32 response)
 				    __releases(&group->notification_lock)
 {
 	bool destroy = false;
@@ -310,9 +310,9 @@ static int process_access_response(struct fsnotify_group *group,
 {
 	struct fanotify_perm_event *event;
 	int fd = response_struct->fd;
-	int response = response_struct->response;
+	__u32 response = response_struct->response;
 
-	pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
+	pr_debug("%s: group=%p fd=%d response=%u\n", __func__, group,
 		 fd, response);
 	/*
 	 * make sure the response is valid, if invalid we do nothing and either
-- 
2.27.0