Re: [PATCH v9 1/1] audio/jack: fix use after free segfault
On Samstag, 7. November 2020 10:58:10 CET Christian Schoenebeck wrote:
> On Samstag, 7. November 2020 01:04:58 CET Geoffrey McRae wrote:
> > This change registers a bottom handler to close the JACK client
> > connection when a server shutdown signal is recieved. Without this
One last minor thing, typo here: "received".
> > libjack2 attempts to "clean up" old clients and causes a use after free
> > segfault.
> >
> > Signed-off-by: Geoffrey McRae
> > ---
> >
> > audio/jackaudio.c | 50 +++
> > 1 file changed, 37 insertions(+), 13 deletions(-)
> >
> > diff --git a/audio/jackaudio.c b/audio/jackaudio.c
> > index 1e714b30bc..e00e19061a 100644
> > --- a/audio/jackaudio.c
> > +++ b/audio/jackaudio.c
> > @@ -25,6 +25,7 @@
> >
> > #include "qemu/osdep.h"
> > #include "qemu/module.h"
> > #include "qemu/atomic.h"
> >
> > +#include "qemu/main-loop.h"
> >
> > #include "qemu-common.h"
> > #include "audio.h"
> >
> > @@ -63,6 +64,7 @@ typedef struct QJackClient {
> >
> > QJackState state;
> > jack_client_t *client;
> > jack_nframes_t freq;
> >
> > +QEMUBH *shutdown_bh;
> >
> > struct QJack *j;
> > int nchannels;
> >
> > @@ -87,6 +89,7 @@ QJackIn;
> >
> > static int qjack_client_init(QJackClient *c);
> > static void qjack_client_connect_ports(QJackClient *c);
> > static void qjack_client_fini(QJackClient *c);
> >
> > +QemuMutex qjack_shutdown_lock;
>
> I think this should be:
>
> static QemuMutex qjack_shutdown_lock;
>
> as this mutex is only accessed from within this unit. Except of that:
>
> Reviewed-by: Christian Schoenebeck
>
> BTW it is common practice to add local functions for initializing,
> destroying, locking and unlocking a specific mutex use case to avoid issues
> when code evolves. But so far the use of this mutex is trivial, so it is Ok
> for now from my PoV.
>
> > static void qjack_buffer_create(QJackBuffer *buffer, int channels, int
> >
> > frames) {
> > @@ -306,21 +309,27 @@ static int qjack_xrun(void *arg)
> >
> > return 0;
> >
> > }
> >
> > +static void qjack_shutdown_bh(void *opaque)
> > +{
> > +QJackClient *c = (QJackClient *)opaque;
> > +qjack_client_fini(c);
> > +}
> > +
> >
> > static void qjack_shutdown(void *arg)
> > {
> >
> > QJackClient *c = (QJackClient *)arg;
> > c->state = QJACK_STATE_SHUTDOWN;
> >
> > +qemu_bh_schedule(c->shutdown_bh);
> >
> > }
> >
> > static void qjack_client_recover(QJackClient *c)
> > {
> >
> > -if (c->state == QJACK_STATE_SHUTDOWN) {
> > -qjack_client_fini(c);
> > +if (c->state != QJACK_STATE_DISCONNECTED) {
> > +return;
> >
> > }
> >
> > /* packets is used simply to throttle this */
> >
> > -if (c->state == QJACK_STATE_DISCONNECTED &&
> > -c->packets % 100 == 0) {
> > +if (c->packets % 100 == 0) {
> >
> > /* if enabled then attempt to recover */
> > if (c->enabled) {
> >
> > @@ -489,15 +498,16 @@ static int qjack_init_out(HWVoiceOut *hw, struct
> > audsettings *as, QJackOut *jo = (QJackOut *)hw;
> >
> > Audiodev *dev = (Audiodev *)drv_opaque;
> >
> > -qjack_client_fini(>c);
> > -
> >
> > jo->c.out = true;
> > jo->c.enabled = false;
> > jo->c.nchannels = as->nchannels;
> > jo->c.opt = dev->u.jack.out;
> >
> > +jo->c.shutdown_bh = qemu_bh_new(qjack_shutdown_bh, >c);
> > +
> >
> > int ret = qjack_client_init(>c);
> > if (ret != 0) {
> >
> > +qemu_bh_delete(jo->c.shutdown_bh);
> >
> > return ret;
> >
> > }
> >
> > @@ -525,15 +535,16 @@ static int qjack_init_in(HWVoiceIn *hw, struct
> > audsettings *as, QJackIn *ji = (QJackIn *)hw;
> >
> > Audiodev *dev = (Audiodev *)drv_opaque;
> >
> > -qjack_client_fini(>c);
> > -
> >
> > ji->c.out = false;
> > ji->c.enabled = false;
> > ji->c.nchannels = as->nchannels;
> > ji->c.opt = dev->u.jack.in;
> >
> > +ji->c.shutdown_bh = qemu_bh_new(qjack_shutdown_bh, >c);
> > +
> >
> > int ret = qjack_client_init(>c);
> > if (ret != 0) {
> >
> > +qemu_bh_delete(ji->c.shutdown_bh);
> >
> > return ret;
> >
> > }
> >
> > @@ -555,7 +566,7 @@ static int qjack_init_in(HWVoiceIn *hw, struct
> > audsettings *as, return 0;
> >
> > }
> >
> > -static void qjack_client_fini(QJackClient *c)
> > +static void qjack_client_fini_locked(QJackClient *c)
> >
> > {
> >
> > switch (c->state) {
> >
> > case QJACK_STATE_RUNNING:
> > @@ -564,28 +575,40 @@ static void qjack_client_fini(QJackClient *c)
> >
> > case QJACK_STATE_SHUTDOWN:
> > jack_client_close(c->client);
> >
> > +c->client = NULL;
> > +
> > +qjack_buffer_free(>fifo);
> > +g_free(c->port);
> > +
> > +c->state = QJACK_STATE_DISCONNECTED;
> >
> > /* fallthrough */
> >
> > case
Re: [PATCH v9 1/1] audio/jack: fix use after free segfault
On Samstag, 7. November 2020 01:04:58 CET Geoffrey McRae wrote:
> This change registers a bottom handler to close the JACK client
> connection when a server shutdown signal is recieved. Without this
> libjack2 attempts to "clean up" old clients and causes a use after free
> segfault.
>
> Signed-off-by: Geoffrey McRae
> ---
> audio/jackaudio.c | 50 +++
> 1 file changed, 37 insertions(+), 13 deletions(-)
>
> diff --git a/audio/jackaudio.c b/audio/jackaudio.c
> index 1e714b30bc..e00e19061a 100644
> --- a/audio/jackaudio.c
> +++ b/audio/jackaudio.c
> @@ -25,6 +25,7 @@
> #include "qemu/osdep.h"
> #include "qemu/module.h"
> #include "qemu/atomic.h"
> +#include "qemu/main-loop.h"
> #include "qemu-common.h"
> #include "audio.h"
>
> @@ -63,6 +64,7 @@ typedef struct QJackClient {
> QJackState state;
> jack_client_t *client;
> jack_nframes_t freq;
> +QEMUBH *shutdown_bh;
>
> struct QJack *j;
> int nchannels;
> @@ -87,6 +89,7 @@ QJackIn;
> static int qjack_client_init(QJackClient *c);
> static void qjack_client_connect_ports(QJackClient *c);
> static void qjack_client_fini(QJackClient *c);
> +QemuMutex qjack_shutdown_lock;
>
I think this should be:
static QemuMutex qjack_shutdown_lock;
as this mutex is only accessed from within this unit. Except of that:
Reviewed-by: Christian Schoenebeck
BTW it is common practice to add local functions for initializing, destroying,
locking and unlocking a specific mutex use case to avoid issues when code
evolves. But so far the use of this mutex is trivial, so it is Ok for now from
my PoV.
> static void qjack_buffer_create(QJackBuffer *buffer, int channels, int
> frames) {
> @@ -306,21 +309,27 @@ static int qjack_xrun(void *arg)
> return 0;
> }
>
> +static void qjack_shutdown_bh(void *opaque)
> +{
> +QJackClient *c = (QJackClient *)opaque;
> +qjack_client_fini(c);
> +}
> +
> static void qjack_shutdown(void *arg)
> {
> QJackClient *c = (QJackClient *)arg;
> c->state = QJACK_STATE_SHUTDOWN;
> +qemu_bh_schedule(c->shutdown_bh);
> }
>
> static void qjack_client_recover(QJackClient *c)
> {
> -if (c->state == QJACK_STATE_SHUTDOWN) {
> -qjack_client_fini(c);
> +if (c->state != QJACK_STATE_DISCONNECTED) {
> +return;
> }
>
> /* packets is used simply to throttle this */
> -if (c->state == QJACK_STATE_DISCONNECTED &&
> -c->packets % 100 == 0) {
> +if (c->packets % 100 == 0) {
>
> /* if enabled then attempt to recover */
> if (c->enabled) {
> @@ -489,15 +498,16 @@ static int qjack_init_out(HWVoiceOut *hw, struct
> audsettings *as, QJackOut *jo = (QJackOut *)hw;
> Audiodev *dev = (Audiodev *)drv_opaque;
>
> -qjack_client_fini(>c);
> -
> jo->c.out = true;
> jo->c.enabled = false;
> jo->c.nchannels = as->nchannels;
> jo->c.opt = dev->u.jack.out;
>
> +jo->c.shutdown_bh = qemu_bh_new(qjack_shutdown_bh, >c);
> +
> int ret = qjack_client_init(>c);
> if (ret != 0) {
> +qemu_bh_delete(jo->c.shutdown_bh);
> return ret;
> }
>
> @@ -525,15 +535,16 @@ static int qjack_init_in(HWVoiceIn *hw, struct
> audsettings *as, QJackIn *ji = (QJackIn *)hw;
> Audiodev *dev = (Audiodev *)drv_opaque;
>
> -qjack_client_fini(>c);
> -
> ji->c.out = false;
> ji->c.enabled = false;
> ji->c.nchannels = as->nchannels;
> ji->c.opt = dev->u.jack.in;
>
> +ji->c.shutdown_bh = qemu_bh_new(qjack_shutdown_bh, >c);
> +
> int ret = qjack_client_init(>c);
> if (ret != 0) {
> +qemu_bh_delete(ji->c.shutdown_bh);
> return ret;
> }
>
> @@ -555,7 +566,7 @@ static int qjack_init_in(HWVoiceIn *hw, struct
> audsettings *as, return 0;
> }
>
> -static void qjack_client_fini(QJackClient *c)
> +static void qjack_client_fini_locked(QJackClient *c)
> {
> switch (c->state) {
> case QJACK_STATE_RUNNING:
> @@ -564,28 +575,40 @@ static void qjack_client_fini(QJackClient *c)
>
> case QJACK_STATE_SHUTDOWN:
> jack_client_close(c->client);
> +c->client = NULL;
> +
> +qjack_buffer_free(>fifo);
> +g_free(c->port);
> +
> +c->state = QJACK_STATE_DISCONNECTED;
> /* fallthrough */
>
> case QJACK_STATE_DISCONNECTED:
> break;
> }
> +}
>
> -qjack_buffer_free(>fifo);
> -g_free(c->port);
> -
> -c->state = QJACK_STATE_DISCONNECTED;
> +static void qjack_client_fini(QJackClient *c)
> +{
> +qemu_mutex_lock(_shutdown_lock);
> +qjack_client_fini_locked(c);
> +qemu_mutex_unlock(_shutdown_lock);
> }
>
> static void qjack_fini_out(HWVoiceOut *hw)
> {
> QJackOut *jo = (QJackOut *)hw;
> qjack_client_fini(>c);
> +
> +qemu_bh_delete(jo->c.shutdown_bh);
> }
>
> static void qjack_fini_in(HWVoiceIn *hw)
> {
> QJackIn *ji = (QJackIn *)hw;
>
[PATCH v9 1/1] audio/jack: fix use after free segfault
This change registers a bottom handler to close the JACK client
connection when a server shutdown signal is recieved. Without this
libjack2 attempts to "clean up" old clients and causes a use after free
segfault.
Signed-off-by: Geoffrey McRae
---
audio/jackaudio.c | 50 +++
1 file changed, 37 insertions(+), 13 deletions(-)
diff --git a/audio/jackaudio.c b/audio/jackaudio.c
index 1e714b30bc..e00e19061a 100644
--- a/audio/jackaudio.c
+++ b/audio/jackaudio.c
@@ -25,6 +25,7 @@
#include "qemu/osdep.h"
#include "qemu/module.h"
#include "qemu/atomic.h"
+#include "qemu/main-loop.h"
#include "qemu-common.h"
#include "audio.h"
@@ -63,6 +64,7 @@ typedef struct QJackClient {
QJackState state;
jack_client_t *client;
jack_nframes_t freq;
+QEMUBH *shutdown_bh;
struct QJack *j;
int nchannels;
@@ -87,6 +89,7 @@ QJackIn;
static int qjack_client_init(QJackClient *c);
static void qjack_client_connect_ports(QJackClient *c);
static void qjack_client_fini(QJackClient *c);
+QemuMutex qjack_shutdown_lock;
static void qjack_buffer_create(QJackBuffer *buffer, int channels, int frames)
{
@@ -306,21 +309,27 @@ static int qjack_xrun(void *arg)
return 0;
}
+static void qjack_shutdown_bh(void *opaque)
+{
+QJackClient *c = (QJackClient *)opaque;
+qjack_client_fini(c);
+}
+
static void qjack_shutdown(void *arg)
{
QJackClient *c = (QJackClient *)arg;
c->state = QJACK_STATE_SHUTDOWN;
+qemu_bh_schedule(c->shutdown_bh);
}
static void qjack_client_recover(QJackClient *c)
{
-if (c->state == QJACK_STATE_SHUTDOWN) {
-qjack_client_fini(c);
+if (c->state != QJACK_STATE_DISCONNECTED) {
+return;
}
/* packets is used simply to throttle this */
-if (c->state == QJACK_STATE_DISCONNECTED &&
-c->packets % 100 == 0) {
+if (c->packets % 100 == 0) {
/* if enabled then attempt to recover */
if (c->enabled) {
@@ -489,15 +498,16 @@ static int qjack_init_out(HWVoiceOut *hw, struct
audsettings *as,
QJackOut *jo = (QJackOut *)hw;
Audiodev *dev = (Audiodev *)drv_opaque;
-qjack_client_fini(>c);
-
jo->c.out = true;
jo->c.enabled = false;
jo->c.nchannels = as->nchannels;
jo->c.opt = dev->u.jack.out;
+jo->c.shutdown_bh = qemu_bh_new(qjack_shutdown_bh, >c);
+
int ret = qjack_client_init(>c);
if (ret != 0) {
+qemu_bh_delete(jo->c.shutdown_bh);
return ret;
}
@@ -525,15 +535,16 @@ static int qjack_init_in(HWVoiceIn *hw, struct
audsettings *as,
QJackIn *ji = (QJackIn *)hw;
Audiodev *dev = (Audiodev *)drv_opaque;
-qjack_client_fini(>c);
-
ji->c.out = false;
ji->c.enabled = false;
ji->c.nchannels = as->nchannels;
ji->c.opt = dev->u.jack.in;
+ji->c.shutdown_bh = qemu_bh_new(qjack_shutdown_bh, >c);
+
int ret = qjack_client_init(>c);
if (ret != 0) {
+qemu_bh_delete(ji->c.shutdown_bh);
return ret;
}
@@ -555,7 +566,7 @@ static int qjack_init_in(HWVoiceIn *hw, struct audsettings
*as,
return 0;
}
-static void qjack_client_fini(QJackClient *c)
+static void qjack_client_fini_locked(QJackClient *c)
{
switch (c->state) {
case QJACK_STATE_RUNNING:
@@ -564,28 +575,40 @@ static void qjack_client_fini(QJackClient *c)
case QJACK_STATE_SHUTDOWN:
jack_client_close(c->client);
+c->client = NULL;
+
+qjack_buffer_free(>fifo);
+g_free(c->port);
+
+c->state = QJACK_STATE_DISCONNECTED;
/* fallthrough */
case QJACK_STATE_DISCONNECTED:
break;
}
+}
-qjack_buffer_free(>fifo);
-g_free(c->port);
-
-c->state = QJACK_STATE_DISCONNECTED;
+static void qjack_client_fini(QJackClient *c)
+{
+qemu_mutex_lock(_shutdown_lock);
+qjack_client_fini_locked(c);
+qemu_mutex_unlock(_shutdown_lock);
}
static void qjack_fini_out(HWVoiceOut *hw)
{
QJackOut *jo = (QJackOut *)hw;
qjack_client_fini(>c);
+
+qemu_bh_delete(jo->c.shutdown_bh);
}
static void qjack_fini_in(HWVoiceIn *hw)
{
QJackIn *ji = (QJackIn *)hw;
qjack_client_fini(>c);
+
+qemu_bh_delete(ji->c.shutdown_bh);
}
static void qjack_enable_out(HWVoiceOut *hw, bool enable)
@@ -662,6 +685,7 @@ static void qjack_info(const char *msg)
static void register_audio_jack(void)
{
+qemu_mutex_init(_shutdown_lock);
audio_driver_register(_driver);
jack_set_thread_creator(qjack_thread_creator);
jack_set_error_function(qjack_error);
--
2.20.1
