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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Mariusz Gorski <marius.gorski@gmail.com>,
	Willy Tarreau <w@1wt.eu>
Subject: [PATCH 4.4 28/28] misc: panel: properly restore atomic counter on error path
Date: Thu, 16 Nov 2017 18:42:46 +0100
Message-ID: <20171116174140.045843632@linuxfoundation.org> (raw)
In-Reply-To: <20171116174138.714641106@linuxfoundation.org>

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

commit 93dc1774d2a4c7a298d5cdf78cc8acdcb7b1428d upstream.

Commit f4757af ("staging: panel: Fix single-open policy race condition")
introduced in 3.19-rc1 attempted to fix a race condition on the open, but
failed to properly do it and used to exit without restoring the semaphore.

This results in -EBUSY being returned after the first open error until
the module is reloaded or the system restarted (ie: consecutive to a
dual open resulting in -EBUSY or to a permission error).

Fixes: f4757af85 # 3.19-rc1
Cc: Mariusz Gorski <marius.gorski@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
[wt: driver is in staging/panel in 4.4]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/panel/panel.c |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

--- a/drivers/staging/panel/panel.c
+++ b/drivers/staging/panel/panel.c
@@ -1431,17 +1431,25 @@ static ssize_t lcd_write(struct file *fi
 
 static int lcd_open(struct inode *inode, struct file *file)
 {
+	int ret;
+
+	ret = -EBUSY;
 	if (!atomic_dec_and_test(&lcd_available))
-		return -EBUSY;	/* open only once at a time */
+		goto fail; /* open only once at a time */
 
+	ret = -EPERM;
 	if (file->f_mode & FMODE_READ)	/* device is write-only */
-		return -EPERM;
+		goto fail;
 
 	if (lcd.must_clear) {
 		lcd_clear_display();
 		lcd.must_clear = false;
 	}
 	return nonseekable_open(inode, file);
+
+ fail:
+	atomic_inc(&lcd_available);
+	return ret;
 }
 
 static int lcd_release(struct inode *inode, struct file *file)
@@ -1704,14 +1712,21 @@ static ssize_t keypad_read(struct file *
 
 static int keypad_open(struct inode *inode, struct file *file)
 {
+	int ret;
+
+	ret = -EBUSY;
 	if (!atomic_dec_and_test(&keypad_available))
-		return -EBUSY;	/* open only once at a time */
+		goto fail;	/* open only once at a time */
 
+	ret = -EPERM;
 	if (file->f_mode & FMODE_WRITE)	/* device is read-only */
-		return -EPERM;
+		goto fail;
 
 	keypad_buflen = 0;	/* flush the buffer on opening */
 	return 0;
+ fail:
+	atomic_inc(&keypad_available);
+	return ret;
 }
 
 static int keypad_release(struct inode *inode, struct file *file)

  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-16 17:42 [PATCH 4.4 00/28] 4.4.99-stable review Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 01/28] mac80211: accept key reinstall without changing anything Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 02/28] mac80211: use constant time comparison with keys Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 03/28] mac80211: dont compare TKIP TX MIC key in reinstall prevention Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 04/28] usb: usbtest: fix NULL pointer dereference Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 05/28] Input: ims-psu - check if CDC union descriptor is sane Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 06/28] ALSA: seq: Cancel pending autoload work at unbinding device Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 07/28] tun/tap: sanitize TUNSETSNDBUF input Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 08/28] tcp: fix tcp_mtu_probe() vs highest_sack Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 09/28] l2tp: check ps->sock before running pppol2tp_session_ioctl() Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 10/28] tun: call dev_get_valid_name() before register_netdevice() Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 11/28] sctp: add the missing sock_owned_by_user check in sctp_icmp_redirect Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 12/28] packet: avoid panic in packet_getsockopt() Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 13/28] ipv6: flowlabel: do not leave opt->tot_len with garbage Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 14/28] net/unix: dont show information about sockets from other namespaces Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 15/28] ip6_gre: only increase err_count for some certain type icmpv6 in ip6gre_err Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 16/28] tun: allow positive return values on dev_get_valid_name() call Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 17/28] sctp: reset owner sk for data chunks on out queues when migrating a sock Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 18/28] ppp: fix race in ppp device destruction Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 19/28] ipip: only increase err_count for some certain type icmp in ipip_err Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 20/28] tcp/dccp: fix ireq->opt races Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 21/28] tcp/dccp: fix lockdep splat in inet_csk_route_req() Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 23/28] security/keys: add CONFIG_KEYS_COMPAT to Kconfig Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 24/28] tipc: fix link attribute propagation bug Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 25/28] brcmfmac: remove setting IBSS mode when stopping AP Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 26/28] target/iscsi: Fix iSCSI task reassignment handling Greg Kroah-Hartman
2017-11-16 17:42 ` [PATCH 4.4 27/28] target: Fix node_acl demo-mode + uncached dynamic shutdown regression Greg Kroah-Hartman
2017-11-16 17:42 ` Greg Kroah-Hartman [this message]
2017-11-16 22:44 ` [PATCH 4.4 00/28] 4.4.99-stable review Shuah Khan
2017-11-17  2:01 ` Guenter Roeck
2017-11-17  8:16 ` natechancellor
2017-11-17  8:26   ` Naresh Kamboju
2017-11-17  8:44     ` Greg Kroah-Hartman
2017-11-17  8:30   ` Greg Kroah-Hartman

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