kernel.git/sound/core/control.c, branch linux-3.2.y

ALSA: core: Fix unexpected error at replacing user TLV

2017-11-11T13:34:30Z

commit 88c54cdf61f508ebcf8da2d819f5dfc03e954d1d upstream. When user tries to replace the user-defined control TLV, the kernel checks the change of its content via memcmp(). The problem is that the kernel passes the return value from memcmp() as is. memcmp() gives a non-zero negative value depending on the comparison result, and this shall be recognized as an error code. The patch covers that corner-case, return 1 properly for the changed TLV. Fixes: 8aa9b586e420 ("[ALSA] Control API - more robust TLV implementation") Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: ctl: Stop notification after disconnection

2016-11-20T01:01:24Z

commit f388cdcdd160687c6650833f286b9c89c50960ff upstream. snd_ctl_remove() has a notification for the removal event. It's superfluous when done during the device got disconnected. Although the notification itself is mostly harmless, it may potentially be harmful, and should be suppressed. Actually some components PCM may free ctl elements during the disconnect or free callbacks, thus it's no theoretical issue. This patch adds the check of card->shutdown flag for avoiding unnecessary notifications after (or during) the disconnect. Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0

2016-02-13T10:34:11Z

commit c0bcdbdff3ff73a54161fca3cb8b6cdbd0bb8762 upstream. When a TLV ioctl with numid zero is handled, the driver may spew a kernel warning with a stack trace at each call. The check was intended obviously only for a kernel driver, but not for a user interaction. Let's fix it. This was spotted by syzkaller fuzzer. Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Add sanity checks for user ctl id name string

2015-05-09T22:16:29Z

commit be3bb8236db2d0fcd705062ae2e2a9d75131222f upstream. There was no check about the id string of user control elements, so we accepted even a control element with an empty string, which is obviously bogus. This patch adds more sanity checks of id strings. Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Make sure that id->index does not overflow

2014-07-11T12:33:52Z

commit 883a1d49f0d77d30012f114b2e19fc141beb3e8e upstream. The ALSA control code expects that the range of assigned indices to a control is continuous and does not overflow. Currently there are no checks to enforce this. If a control with a overflowing index range is created that control becomes effectively inaccessible and unremovable since snd_ctl_find_id() will not be able to find it. This patch adds a check that makes sure that controls with a overflowing index range can not be created. Signed-off-by: Lars-Peter Clausen Acked-by: Jaroslav Kysela Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Handle numid overflow

2014-07-11T12:33:52Z

commit ac902c112d90a89e59916f751c2745f4dbdbb4bd upstream. Each control gets automatically assigned its numids when the control is created. The allocation is done by incrementing the numid by the amount of allocated numids per allocation. This means that excessive creation and destruction of controls (e.g. via SNDRV_CTL_IOCTL_ELEM_ADD/REMOVE) can cause the id to eventually overflow. Currently when this happens for the control that caused the overflow kctl->id.numid + kctl->count will also over flow causing it to be smaller than kctl->id.numid. Most of the code assumes that this is something that can not happen, so we need to make sure that it won't happen Signed-off-by: Lars-Peter Clausen Acked-by: Jaroslav Kysela Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Don't access controls outside of protected regions

2014-07-11T12:33:51Z

commit fd9f26e4eca5d08a27d12c0933fceef76ed9663d upstream. A control that is visible on the card->controls list can be freed at any time. This means we must not access any of its memory while not holding the controls_rw_lock. Otherwise we risk a use after free access. Signed-off-by: Lars-Peter Clausen Acked-by: Jaroslav Kysela Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Fix replacing user controls

2014-07-11T12:33:51Z

commit 82262a46627bebb0febcc26664746c25cef08563 upstream. There are two issues with the current implementation for replacing user controls. The first is that the code does not check if the control is actually a user control and neither does it check if the control is owned by the process that tries to remove it. That allows userspace applications to remove arbitrary controls, which can cause a user after free if a for example a driver does not expect a control to be removed from under its feed. The second issue is that on one hand when a control is replaced the user_ctl_count limit is not checked and on the other hand the user_ctl_count is increased (even though the number of user controls does not change). This allows userspace, once the user_ctl_count limit as been reached, to repeatedly replace a control until user_ctl_count overflows. Once that happens new controls can be added effectively bypassing the user_ctl_count limit. Both issues can be fixed by instead of open-coding the removal of the control that is to be replaced to use snd_ctl_remove_user_ctl(). This function does proper permission checks as well as decrements user_ctl_count after the control has been removed. Note that by using snd_ctl_remove_user_ctl() the check which returns -EBUSY at beginning of the function if the control already exists is removed. This is not a problem though since the check is quite useless, because the lock that is protecting the control list is released between the check and before adding the new control to the list, which means that it is possible that a different control with the same settings is added to the list after the check. Luckily there is another check that is done while holding the lock in snd_ctl_add(), so we'll rely on that to make sure that the same control is not added twice. Signed-off-by: Lars-Peter Clausen Acked-by: Jaroslav Kysela Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: control: Protect user controls against concurrent access

2014-07-11T12:33:51Z

commit 07f4d9d74a04aa7c72c5dae0ef97565f28f17b92 upstream. The user-control put and get handlers as well as the tlv do not protect against concurrent access from multiple threads. Since the state of the control is not updated atomically it is possible that either two write operations or a write and a read operation race against each other. Both can lead to arbitrary memory disclosure. This patch introduces a new lock that protects user-controls from concurrent access. Since applications typically access controls sequentially than in parallel a single lock per card should be fine. Signed-off-by: Lars-Peter Clausen Acked-by: Jaroslav Kysela Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: Avoid endless sleep after disconnect

2012-11-16T16:46:50Z

commit 0914f7961babbf28aaa2f19b453951fb4841c03f upstream. When disconnect callback is called, each component should wake up sleepers and check card->shutdown flag for avoiding the endless sleep blocking the proper resource release. Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings