diff mbox series

[net,3/4] can: can327: flush TX_work on ldisc .close()

Message ID 20221207105243.2483884-4-mkl@pengutronix.de (mailing list archive)
State Accepted
Commit f4a4d121ebecaa6f396f21745ce97de014281ccc
Delegated to: Netdev Maintainers
Headers show
Series [net,1/4] can: af_can: fix NULL pointer dereference in can_rcv_filter | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Pull request is its own cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers fail 1 blamed authors not CCed: mailhol.vincent@wanadoo.fr; 1 maintainers not CCed: mailhol.vincent@wanadoo.fr
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch warning WARNING: Duplicate signature
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Marc Kleine-Budde Dec. 7, 2022, 10:52 a.m. UTC 
From: Max Staudt <max@enpas.org>

Additionally, remove it from .ndo_stop().

This ensures that the worker is not called after being freed, and that
the UART TX queue remains active to send final commands when the
netdev is stopped.

Thanks to Jiri Slaby for finding this in slcan:

  https://lore.kernel.org/linux-can/20221201073426.17328-1-jirislaby@kernel.org/

A variant of this patch for slcan, with the flush in .ndo_stop() still
present, has been tested successfully on physical hardware:

  https://bugzilla.suse.com/show_bug.cgi?id=1205597

Fixes: 43da2f07622f ("can: can327: CAN/ldisc driver for ELM327 based OBD-II adapters")
Cc: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Max Staudt <max@enpas.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Max Staudt <max@enpas.org>
Link: https://lore.kernel.org/all/20221202160148.282564-1-max@enpas.org
Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/can327.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/can/can327.c b/drivers/net/can/can327.c
index ed3d0b8989a0..dc7192ecb001 100644
--- a/drivers/net/can/can327.c
+++ b/drivers/net/can/can327.c
@@ -796,9 +796,9 @@  static int can327_netdev_close(struct net_device *dev)
 
 	netif_stop_queue(dev);
 
-	/* Give UART one final chance to flush. */
-	clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
-	flush_work(&elm->tx_work);
+	/* We don't flush the UART TX queue here, as we want final stop
+	 * commands (like the above dummy char) to be flushed out.
+	 */
 
 	can_rx_offload_disable(&elm->offload);
 	elm->can.state = CAN_STATE_STOPPED;
@@ -1069,12 +1069,15 @@  static void can327_ldisc_close(struct tty_struct *tty)
 {
 	struct can327 *elm = (struct can327 *)tty->disc_data;
 
-	/* unregister_netdev() calls .ndo_stop() so we don't have to.
-	 * Our .ndo_stop() also flushes the TTY write wakeup handler,
-	 * so we can safely set elm->tty = NULL after this.
-	 */
+	/* unregister_netdev() calls .ndo_stop() so we don't have to. */
 	unregister_candev(elm->dev);
 
+	/* Give UART one final chance to flush.
+	 * No need to clear TTY_DO_WRITE_WAKEUP since .write_wakeup() is
+	 * serialised against .close() and will not be called once we return.
+	 */
+	flush_work(&elm->tx_work);
+
 	/* Mark channel as dead */
 	spin_lock_bh(&elm->lock);
 	tty->disc_data = NULL;