This is a note to let you know that I've just added the patch titled
ALSA: seq: Fix double port list deletion
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-seq-fix-double-port-list-deletion.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 13d5e5d4725c64ec06040d636832e78453f477b7 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Tue, 16 Feb 2016 14:15:59 +0100
Subject: ALSA: seq: Fix double port list deletion
From: Takashi Iwai <tiwai@xxxxxxx>
commit 13d5e5d4725c64ec06040d636832e78453f477b7 upstream.
The commit [7f0973e973cd: ALSA: seq: Fix lockdep warnings due to
double mutex locks] split the management of two linked lists (source
and destination) into two individual calls for avoiding the AB/BA
deadlock. However, this may leave the possible double deletion of one
of two lists when the counterpart is being deleted concurrently.
It ends up with a list corruption, as revealed by syzkaller fuzzer.
This patch fixes it by checking the list emptiness and skipping the
deletion and the following process.
BugLink: http://lkml.kernel.org/r/CACT4Y+bay9qsrz6dQu31EcGaH9XwfW7o3oBzSQUG9fMszoh=Sg@xxxxxxxxxxxxxx
Fixes: 7f0973e973cd ('ALSA: seq: Fix lockdep warnings due to 'double mutex locks)
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/seq/seq_ports.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
--- a/sound/core/seq/seq_ports.c
+++ b/sound/core/seq/seq_ports.c
@@ -540,19 +540,22 @@ static void delete_and_unsubscribe_port(
bool is_src, bool ack)
{
struct snd_seq_port_subs_info *grp;
+ struct list_head *list;
+ bool empty;
grp = is_src ? &port->c_src : &port->c_dest;
+ list = is_src ? &subs->src_list : &subs->dest_list;
down_write(&grp->list_mutex);
write_lock_irq(&grp->list_lock);
- if (is_src)
- list_del(&subs->src_list);
- else
- list_del(&subs->dest_list);
+ empty = list_empty(list);
+ if (!empty)
+ list_del_init(list);
grp->exclusive = 0;
write_unlock_irq(&grp->list_lock);
up_write(&grp->list_mutex);
- unsubscribe_port(client, port, grp, &subs->info, ack);
+ if (!empty)
+ unsubscribe_port(client, port, grp, &subs->info, ack);
}
/* connect two ports */
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-3.10/input-elantech-add-fujitsu-lifebook-u745-to-force-crc_enabled.patch
queue-3.10/alsa-seq-fix-double-port-list-deletion.patch
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