This is a note to let you know that I've just added the patch titled ALSA: timer: Fix race at concurrent reads 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-race-at-concurrent-reads.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@xxxxxxxxxxxxxxx> know about it. >From 4dff5c7b7093b19c19d3a100f8a3ad87cb7cd9e7 Mon Sep 17 00:00:00 2001 From: Takashi Iwai <tiwai@xxxxxxx> Date: Mon, 8 Feb 2016 17:26:58 +0100 Subject: ALSA: timer: Fix race at concurrent reads From: Takashi Iwai <tiwai@xxxxxxx> commit 4dff5c7b7093b19c19d3a100f8a3ad87cb7cd9e7 upstream. snd_timer_user_read() has a potential race among parallel reads, as qhead and qused are updated outside the critical section due to copy_to_user() calls. Move them into the critical section, and also sanitize the relevant code a bit. Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/core/timer.c | 34 +++++++++++++++------------------- 1 file changed, 15 insertions(+), 19 deletions(-) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1926,6 +1926,7 @@ static ssize_t snd_timer_user_read(struc { struct snd_timer_user *tu; long result = 0, unit; + int qhead; int err = 0; tu = file->private_data; @@ -1937,7 +1938,7 @@ static ssize_t snd_timer_user_read(struc if ((file->f_flags & O_NONBLOCK) != 0 || result > 0) { err = -EAGAIN; - break; + goto _error; } set_current_state(TASK_INTERRUPTIBLE); @@ -1952,42 +1953,37 @@ static ssize_t snd_timer_user_read(struc if (tu->disconnected) { err = -ENODEV; - break; + goto _error; } if (signal_pending(current)) { err = -ERESTARTSYS; - break; + goto _error; } } + qhead = tu->qhead++; + tu->qhead %= tu->queue_size; spin_unlock_irq(&tu->qlock); - if (err < 0) - goto _error; if (tu->tread) { - if (copy_to_user(buffer, &tu->tqueue[tu->qhead++], - sizeof(struct snd_timer_tread))) { + if (copy_to_user(buffer, &tu->tqueue[qhead], + sizeof(struct snd_timer_tread))) err = -EFAULT; - goto _error; - } } else { - if (copy_to_user(buffer, &tu->queue[tu->qhead++], - sizeof(struct snd_timer_read))) { + if (copy_to_user(buffer, &tu->queue[qhead], + sizeof(struct snd_timer_read))) err = -EFAULT; - goto _error; - } } - tu->qhead %= tu->queue_size; - - result += unit; - buffer += unit; - spin_lock_irq(&tu->qlock); tu->qused--; + if (err < 0) + goto _error; + result += unit; + buffer += unit; } - spin_unlock_irq(&tu->qlock); _error: + spin_unlock_irq(&tu->qlock); return result > 0 ? result : err; } Patches currently in stable-queue which might be from tiwai@xxxxxxx are queue-4.4/alsa-seq-fix-race-at-closing-in-virmidi-driver.patch queue-4.4/alsa-hda-fix-bad-dereference-of-jack-object.patch queue-4.4/alsa-usb-audio-add-quirk-for-microsoft-lifecam-hd-6000.patch queue-4.4/alsa-rawmidi-remove-kernel-warning-for-null-user-space-buffer-check.patch queue-4.4/alsa-usb-audio-fix-oppo-ha-1-vendor-id.patch queue-4.4/alsa-timer-fix-race-at-concurrent-reads.patch queue-4.4/alsa-hda-realtek-support-dell-headset-mode-for-alc225.patch queue-4.4/alsa-hda-fix-static-checker-warning-in-patch_hdmi.c.patch queue-4.4/alsa-seq-fix-lockdep-warnings-due-to-double-mutex-locks.patch queue-4.4/alsa-usb-audio-fix-teac-ud-501-ud-503-nt-503-usb-delay.patch queue-4.4/alsa-timer-fix-wrong-instance-passed-to-slave-callbacks.patch queue-4.4/alsa-hda-disable-dynamic-clock-gating-on-broxton-before-reset.patch queue-4.4/alsa-hda-realtek-support-headset-mode-for-alc225.patch queue-4.4/alsa-hda-implement-loopback-control-switch-for-realtek-and-other-codecs.patch queue-4.4/alsa-hda-realtek-new-codec-support-of-alc225.patch queue-4.4/alsa-seq-degrade-the-error-message-for-too-many-opens.patch queue-4.4/alsa-compress-disable-get_codec_caps-ioctl-for-some-architectures.patch queue-4.4/alsa-rawmidi-make-snd_rawmidi_transmit-race-free.patch queue-4.4/alsa-hda-fix-speaker-output-from-vaio-aio-machines.patch queue-4.4/alsa-bebob-use-a-signed-return-type-for-get_formation_index.patch queue-4.4/alsa-add-missing-dependency-on-config_snd_timer.patch queue-4.4/alsa-dummy-implement-timer-backend-switching-more-safely.patch queue-4.4/alsa-dummy-disable-switching-timer-backend-via-sysfs.patch queue-4.4/alsa-seq-fix-incorrect-sanity-check-at-snd_seq_oss_synth_cleanup.patch queue-4.4/alsa-seq-fix-yet-another-races-among-alsa-timer-accesses.patch queue-4.4/alsa-usb-audio-avoid-freeing-umidi-object-twice.patch queue-4.4/revert-alsa-hda-fix-noise-on-gigabyte-z170x-mobo.patch queue-4.4/alsa-hda-add-fixup-for-mac-mini-7-1-model.patch queue-4.4/alsa-usb-audio-add-native-dsd-support-for-ps-audio-nuwave-dac.patch queue-4.4/alsa-timer-fix-leftover-link-at-closing.patch queue-4.4/alsa-rawmidi-fix-race-at-copying-updating-the-position.patch queue-4.4/alsa-pcm-fix-potential-deadlock-in-oss-emulation.patch queue-4.4/alsa-timer-fix-link-corruption-due-to-double-start-or-stop.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html