Patch "ALSA: timer: Fix missing queue indices reset at SNDRV_TIMER_IOCTL_SELECT" has been added to the 4.4-stable tree

Patch "ALSA: timer: Fix missing queue indices reset at SNDRV_TIMER_IOCTL_SELECT" has been added to the 4.4-stable tree

[gregkh]

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 4.4-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-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ba3021b2c79b2fa9114f92790a99deb27a65b728 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
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@suse.de>

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@google.com>
Tested-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/timer.c |    1 +
 1 file changed, 1 insertion(+)

--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -1621,6 +1621,7 @@ 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@suse.de are

queue-4.4/alsa-timer-fix-race-between-read-and-ioctl.patch
queue-4.4/alsa-timer-fix-missing-queue-indices-reset-at-sndrv_timer_ioctl_select.patch
queue-4.4/asoc-fix-use-after-free-at-card-unregistration.patch
queue-4.4/ptrace-properly-initialize-ptracer_cred-on-fork.patch