This is a note to let you know that I've just added the patch titled
ALSA: timer: Fix missing queue indices reset at SNDRV_TIMER_IOCTL_SELECT
to the 4.9-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-timer-fix-missing-queue-indices-reset-at-sndrv_timer_ioctl_select.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ba3021b2c79b2fa9114f92790a99deb27a65b728 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Fri, 2 Jun 2017 17:26:56 +0200
Subject: ALSA: timer: Fix missing queue indices reset at SNDRV_TIMER_IOCTL_SELECT
From: Takashi Iwai <tiwai@xxxxxxx>
commit ba3021b2c79b2fa9114f92790a99deb27a65b728 upstream.
snd_timer_user_tselect() reallocates the queue buffer dynamically, but
it forgot to reset its indices. Since the read may happen
concurrently with ioctl and snd_timer_user_tselect() allocates the
buffer via kmalloc(), this may lead to the leak of uninitialized
kernel-space data, as spotted via KMSAN:
BUG: KMSAN: use of unitialized memory in snd_timer_user_read+0x6c4/0xa10
CPU: 0 PID: 1037 Comm: probe Not tainted 4.11.0-rc5+ #2739
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16
dump_stack+0x143/0x1b0 lib/dump_stack.c:52
kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:1007
kmsan_check_memory+0xc2/0x140 mm/kmsan/kmsan.c:1086
copy_to_user ./arch/x86/include/asm/uaccess.h:725
snd_timer_user_read+0x6c4/0xa10 sound/core/timer.c:2004
do_loop_readv_writev fs/read_write.c:716
__do_readv_writev+0x94c/0x1380 fs/read_write.c:864
do_readv_writev fs/read_write.c:894
vfs_readv fs/read_write.c:908
do_readv+0x52a/0x5d0 fs/read_write.c:934
SYSC_readv+0xb6/0xd0 fs/read_write.c:1021
SyS_readv+0x87/0xb0 fs/read_write.c:1018
This patch adds the missing reset of queue indices. Together with the
previous fix for the ioctl/read race, we cover the whole problem.
Reported-by: Alexander Potapenko <glider@xxxxxxxxxx>
Tested-by: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/timer.c | 1 +
1 file changed, 1 insertion(+)
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -1622,6 +1622,7 @@ static int snd_timer_user_tselect(struct
if (err < 0)
goto __err;
+ tu->qhead = tu->qtail = tu->qused = 0;
kfree(tu->queue);
tu->queue = NULL;
kfree(tu->tqueue);
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-4.9/alsa-timer-fix-race-between-read-and-ioctl.patch
queue-4.9/alsa-timer-fix-missing-queue-indices-reset-at-sndrv_timer_ioctl_select.patch
queue-4.9/asoc-fix-use-after-free-at-card-unregistration.patch
queue-4.9/ptrace-properly-initialize-ptracer_cred-on-fork.patch