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74 lines
2.5 KiB
Diff
74 lines
2.5 KiB
Diff
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From d11662f4f798b50d8c8743f433842c3e40fe3378 Mon Sep 17 00:00:00 2001
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From: Takashi Iwai <tiwai@suse.de>
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Date: Fri, 2 Jun 2017 15:03:38 +0200
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Subject: ALSA: timer: Fix race between read and ioctl
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The read from ALSA timer device, the function snd_timer_user_tread(),
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may access to an uninitialized struct snd_timer_user fields when the
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read is concurrently performed while the ioctl like
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snd_timer_user_tselect() is invoked. We have already fixed the races
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among ioctls via a mutex, but we seem to have forgotten the race
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between read vs ioctl.
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This patch simply applies (more exactly extends the already applied
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range of) tu->ioctl_lock in snd_timer_user_tread() for closing the
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race window.
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Reported-by: Alexander Potapenko <glider@google.com>
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Tested-by: Alexander Potapenko <glider@google.com>
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Cc: <stable@vger.kernel.org>
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Signed-off-by: Takashi Iwai <tiwai@suse.de>
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---
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sound/core/timer.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/sound/core/timer.c b/sound/core/timer.c
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index 2f836ca..1118bd8 100644
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--- a/sound/core/timer.c
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+++ b/sound/core/timer.c
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@@ -1959,6 +1959,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
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tu = file->private_data;
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unit = tu->tread ? sizeof(struct snd_timer_tread) : sizeof(struct snd_timer_read);
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+ mutex_lock(&tu->ioctl_lock);
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spin_lock_irq(&tu->qlock);
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while ((long)count - result >= unit) {
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while (!tu->qused) {
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@@ -1974,7 +1975,9 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
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add_wait_queue(&tu->qchange_sleep, &wait);
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spin_unlock_irq(&tu->qlock);
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+ mutex_unlock(&tu->ioctl_lock);
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schedule();
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+ mutex_lock(&tu->ioctl_lock);
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spin_lock_irq(&tu->qlock);
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remove_wait_queue(&tu->qchange_sleep, &wait);
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@@ -1994,7 +1997,6 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
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tu->qused--;
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spin_unlock_irq(&tu->qlock);
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- mutex_lock(&tu->ioctl_lock);
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if (tu->tread) {
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if (copy_to_user(buffer, &tu->tqueue[qhead],
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sizeof(struct snd_timer_tread)))
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@@ -2004,7 +2006,6 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
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sizeof(struct snd_timer_read)))
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err = -EFAULT;
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}
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- mutex_unlock(&tu->ioctl_lock);
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spin_lock_irq(&tu->qlock);
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if (err < 0)
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@@ -2014,6 +2015,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
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}
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_error:
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spin_unlock_irq(&tu->qlock);
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+ mutex_unlock(&tu->ioctl_lock);
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return result > 0 ? result : err;
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}
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--
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cgit v1.1
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