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From aa1655b3ee03db5fde1bdfd4a64e6fa8c9011d53 Mon Sep 17 00:00:00 2001
From: Jiri Slaby <jslaby@suse.cz>
Date: Thu, 26 Nov 2015 19:28:26 +0100
Subject: [PATCH 1/2] TTY: n_hdlc, fix lockdep false positive
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.
Upstream-Status: Backport
[We need this patch to be able to cherry-pick the patch for
CVE-2017-2636 from later version.]
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
---
drivers/tty/n_hdlc.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)
diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
index 1b2db9a..f26657c 100644
--- 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);
@@ -855,10 +854,10 @@ static struct n_hdlc *n_hdlc_alloc(void)
memset(n_hdlc, 0, sizeof(*n_hdlc));
- 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++) {
@@ -887,16 +886,6 @@ 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
--
1.9.1
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