From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>,
Dmitry Vyukov <dvyukov@google.com>
Subject: [PATCH 4.4 01/36] TTY: n_hdlc, fix lockdep false positive
Date: Mon, 13 Mar 2017 16:39:01 +0800 [thread overview]
Message-ID: <20170313083352.613621959@linuxfoundation.org> (raw)
In-Reply-To: <20170313083352.550085638@linuxfoundation.org>
4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Slaby <jslaby@suse.cz>
commit e9b736d88af1a143530565929390cadf036dc799 upstream.
The class of 4 n_hdls buf locks is the same because a single function
n_hdlc_buf_list_init is used to init all the locks. But since
flush_tx_queue takes n_hdlc->tx_buf_list.spinlock and then calls
n_hdlc_buf_put which takes n_hdlc->tx_free_buf_list.spinlock, lockdep
emits a warning:
=============================================
[ INFO: possible recursive locking detected ]
4.3.0-25.g91e30a7-default #1 Not tainted
---------------------------------------------
a.out/1248 is trying to acquire lock:
(&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fd020>] n_hdlc_buf_put+0x20/0x60 [n_hdlc]
but task is already holding lock:
(&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fdc07>] n_hdlc_tty_ioctl+0x127/0x1d0 [n_hdlc]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&(&list->spinlock)->rlock);
lock(&(&list->spinlock)->rlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by a.out/1248:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff814c9eb0>] tty_ldisc_ref_wait+0x20/0x50
#1: (&(&list->spinlock)->rlock){......}, at: [<ffffffffa01fdc07>] n_hdlc_tty_ioctl+0x127/0x1d0 [n_hdlc]
...
Call Trace:
...
[<ffffffff81738fd0>] _raw_spin_lock_irqsave+0x50/0x70
[<ffffffffa01fd020>] n_hdlc_buf_put+0x20/0x60 [n_hdlc]
[<ffffffffa01fdc24>] n_hdlc_tty_ioctl+0x144/0x1d0 [n_hdlc]
[<ffffffff814c25c1>] tty_ioctl+0x3f1/0xe40
...
Fix it by initializing the spin_locks separately. This removes also
reduntand memset of a freshly kzallocated space.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/n_hdlc.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)
--- a/drivers/tty/n_hdlc.c
+++ b/drivers/tty/n_hdlc.c
@@ -159,7 +159,6 @@ struct n_hdlc {
/*
* HDLC buffer list manipulation functions
*/
-static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
struct n_hdlc_buf *buf);
static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
@@ -853,10 +852,10 @@ static struct n_hdlc *n_hdlc_alloc(void)
if (!n_hdlc)
return NULL;
- n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
- n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
- n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
- n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
+ spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
+ spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
+ spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
+ spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
/* allocate free rx buffer list */
for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
@@ -885,16 +884,6 @@ static struct n_hdlc *n_hdlc_alloc(void)
} /* end of n_hdlc_alloc() */
/**
- * n_hdlc_buf_list_init - initialize specified HDLC buffer list
- * @list - pointer to buffer list
- */
-static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
-{
- memset(list, 0, sizeof(*list));
- spin_lock_init(&list->spinlock);
-} /* end of n_hdlc_buf_list_init() */
-
-/**
* n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
* @list - pointer to buffer list
* @buf - pointer to buffer
next prev parent reply other threads:[~2017-03-13 8:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-13 8:39 [PATCH 4.4 00/36] 4.4.54-stable review Greg Kroah-Hartman
2017-03-13 8:39 ` Greg Kroah-Hartman [this message]
2017-03-13 8:39 ` [PATCH 4.4 02/36] tty: n_hdlc: get rid of racy n_hdlc.tbuf Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 03/36] serial: 8250_pci: Add MKS Tenta SCOM-0800 and SCOM-0801 cards Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 04/36] KVM: s390: Disable dirty log retrieval for UCONTROL guests Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 05/36] KVM: VMX: use correct vmcs_read/write for guest segment selector/base Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 06/36] Bluetooth: Add another AR3012 04ca:3018 device Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 07/36] s390/qdio: clear DSCI prior to scanning multiple input queues Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 08/36] s390/dcssblk: fix device size calculation in dcssblk_direct_access() Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 09/36] s390: TASK_SIZE for kernel threads Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 10/36] s390: make setup_randomness work Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 11/36] s390: use correct input data address for setup_randomness Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 12/36] net: mvpp2: fix DMA address calculation in mvpp2_txq_inc_put() Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 13/36] mnt: Tuck mounts under others instead of creating shadow/side mounts Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 14/36] IB/ipoib: Fix deadlock between rmmod and set_mode Greg Kroah-Hartman
2017-03-17 2:24 ` Ben Hutchings
2017-03-13 8:39 ` [PATCH 4.4 15/36] IB/IPoIB: Add destination address when re-queue packet Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 16/36] IB/srp: Avoid that duplicate responses trigger a kernel bug Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 17/36] IB/srp: Fix race conditions related to task management Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 18/36] ktest: Fix child exit code processing Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 19/36] ceph: remove req from unsafe list when unregistering it Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 20/36] target: Fix NULL dereference during LUN lookup + active I/O shutdown Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 21/36] nlm: Ensure callback code also checks that the files match Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 22/36] pwm: pca9685: Fix period change with same duty cycle Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 23/36] xtensa: move parse_tag_fdt out of #ifdef CONFIG_BLK_DEV_INITRD Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 24/36] mac80211: flush delayed work when entering suspend Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 26/36] drm/ast: Fix test for VGA enabled Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 27/36] drm/ast: Call open_key before enable_mmio in POST code Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 28/36] drm/ast: Fix AST2400 POST failure without BMC FW or VBIOS Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 31/36] drm/atomic: fix an error code in mode_fixup() Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 32/36] fakelb: fix schedule while atomic Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 34/36] libceph: use BUG() instead of BUG_ON(1) Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 35/36] fat: fix using uninitialized fields of fat_inode/fsinfo_inode Greg Kroah-Hartman
2017-03-13 8:39 ` [PATCH 4.4 36/36] drivers: hv: Turn off write permission on the hypercall page Greg Kroah-Hartman
2017-03-13 22:36 ` [PATCH 4.4 00/36] 4.4.54-stable review Guenter Roeck
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