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linux/sound/core/misc.c
Takashi Iwai ef34a0ae7a ALSA: core: Add async signal helpers
Currently the call of kill_fasync() from an interrupt handler might
lead to potential spin deadlocks, as spotted by syzkaller.
Unfortunately, it's not so trivial to fix this lock chain as it's
involved with the tasklist_lock that is touched in allover places.

As a temporary workaround, this patch provides the way to defer the
async signal notification in a work.  The new helper functions,
snd_fasync_helper() and snd_kill_faync() are replacements for
fasync_helper() and kill_fasync(), respectively.  In addition,
snd_fasync_free() needs to be called at the destructor of the relevant
file object.

Link: https://lore.kernel.org/r/20220728125945.29533-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2022-07-29 12:57:10 +02:00

242 lines
5.8 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Misc and compatibility things
* Copyright (c) by Jaroslav Kysela <perex@perex.cz>
*/
#include <linux/init.h>
#include <linux/export.h>
#include <linux/moduleparam.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/fs.h>
#include <sound/core.h>
#ifdef CONFIG_SND_DEBUG
#ifdef CONFIG_SND_DEBUG_VERBOSE
#define DEFAULT_DEBUG_LEVEL 2
#else
#define DEFAULT_DEBUG_LEVEL 1
#endif
static int debug = DEFAULT_DEBUG_LEVEL;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "Debug level (0 = disable)");
#endif /* CONFIG_SND_DEBUG */
void release_and_free_resource(struct resource *res)
{
if (res) {
release_resource(res);
kfree(res);
}
}
EXPORT_SYMBOL(release_and_free_resource);
#ifdef CONFIG_SND_VERBOSE_PRINTK
/* strip the leading path if the given path is absolute */
static const char *sanity_file_name(const char *path)
{
if (*path == '/')
return strrchr(path, '/') + 1;
else
return path;
}
#endif
#if defined(CONFIG_SND_DEBUG) || defined(CONFIG_SND_VERBOSE_PRINTK)
void __snd_printk(unsigned int level, const char *path, int line,
const char *format, ...)
{
va_list args;
#ifdef CONFIG_SND_VERBOSE_PRINTK
int kern_level;
struct va_format vaf;
char verbose_fmt[] = KERN_DEFAULT "ALSA %s:%d %pV";
bool level_found = false;
#endif
#ifdef CONFIG_SND_DEBUG
if (debug < level)
return;
#endif
va_start(args, format);
#ifdef CONFIG_SND_VERBOSE_PRINTK
vaf.fmt = format;
vaf.va = &args;
while ((kern_level = printk_get_level(vaf.fmt)) != 0) {
const char *end_of_header = printk_skip_level(vaf.fmt);
/* Ignore KERN_CONT. We print filename:line for each piece. */
if (kern_level >= '0' && kern_level <= '7') {
memcpy(verbose_fmt, vaf.fmt, end_of_header - vaf.fmt);
level_found = true;
}
vaf.fmt = end_of_header;
}
if (!level_found && level)
memcpy(verbose_fmt, KERN_DEBUG, sizeof(KERN_DEBUG) - 1);
printk(verbose_fmt, sanity_file_name(path), line, &vaf);
#else
vprintk(format, args);
#endif
va_end(args);
}
EXPORT_SYMBOL_GPL(__snd_printk);
#endif
#ifdef CONFIG_PCI
#include <linux/pci.h>
/**
* snd_pci_quirk_lookup_id - look up a PCI SSID quirk list
* @vendor: PCI SSV id
* @device: PCI SSD id
* @list: quirk list, terminated by a null entry
*
* Look through the given quirk list and finds a matching entry
* with the same PCI SSID. When subdevice is 0, all subdevice
* values may match.
*
* Returns the matched entry pointer, or NULL if nothing matched.
*/
const struct snd_pci_quirk *
snd_pci_quirk_lookup_id(u16 vendor, u16 device,
const struct snd_pci_quirk *list)
{
const struct snd_pci_quirk *q;
for (q = list; q->subvendor || q->subdevice; q++) {
if (q->subvendor != vendor)
continue;
if (!q->subdevice ||
(device & q->subdevice_mask) == q->subdevice)
return q;
}
return NULL;
}
EXPORT_SYMBOL(snd_pci_quirk_lookup_id);
/**
* snd_pci_quirk_lookup - look up a PCI SSID quirk list
* @pci: pci_dev handle
* @list: quirk list, terminated by a null entry
*
* Look through the given quirk list and finds a matching entry
* with the same PCI SSID. When subdevice is 0, all subdevice
* values may match.
*
* Returns the matched entry pointer, or NULL if nothing matched.
*/
const struct snd_pci_quirk *
snd_pci_quirk_lookup(struct pci_dev *pci, const struct snd_pci_quirk *list)
{
if (!pci)
return NULL;
return snd_pci_quirk_lookup_id(pci->subsystem_vendor,
pci->subsystem_device,
list);
}
EXPORT_SYMBOL(snd_pci_quirk_lookup);
#endif
/*
* Deferred async signal helpers
*
* Below are a few helper functions to wrap the async signal handling
* in the deferred work. The main purpose is to avoid the messy deadlock
* around tasklist_lock and co at the kill_fasync() invocation.
* fasync_helper() and kill_fasync() are replaced with snd_fasync_helper()
* and snd_kill_fasync(), respectively. In addition, snd_fasync_free() has
* to be called at releasing the relevant file object.
*/
struct snd_fasync {
struct fasync_struct *fasync;
int signal;
int poll;
int on;
struct list_head list;
};
static DEFINE_SPINLOCK(snd_fasync_lock);
static LIST_HEAD(snd_fasync_list);
static void snd_fasync_work_fn(struct work_struct *work)
{
struct snd_fasync *fasync;
spin_lock_irq(&snd_fasync_lock);
while (!list_empty(&snd_fasync_list)) {
fasync = list_first_entry(&snd_fasync_list, struct snd_fasync, list);
list_del_init(&fasync->list);
spin_unlock_irq(&snd_fasync_lock);
if (fasync->on)
kill_fasync(&fasync->fasync, fasync->signal, fasync->poll);
spin_lock_irq(&snd_fasync_lock);
}
spin_unlock_irq(&snd_fasync_lock);
}
static DECLARE_WORK(snd_fasync_work, snd_fasync_work_fn);
int snd_fasync_helper(int fd, struct file *file, int on,
struct snd_fasync **fasyncp)
{
struct snd_fasync *fasync = NULL;
if (on) {
fasync = kzalloc(sizeof(*fasync), GFP_KERNEL);
if (!fasync)
return -ENOMEM;
INIT_LIST_HEAD(&fasync->list);
}
spin_lock_irq(&snd_fasync_lock);
if (*fasyncp) {
kfree(fasync);
fasync = *fasyncp;
} else {
if (!fasync) {
spin_unlock_irq(&snd_fasync_lock);
return 0;
}
*fasyncp = fasync;
}
fasync->on = on;
spin_unlock_irq(&snd_fasync_lock);
return fasync_helper(fd, file, on, &fasync->fasync);
}
EXPORT_SYMBOL_GPL(snd_fasync_helper);
void snd_kill_fasync(struct snd_fasync *fasync, int signal, int poll)
{
unsigned long flags;
if (!fasync || !fasync->on)
return;
spin_lock_irqsave(&snd_fasync_lock, flags);
fasync->signal = signal;
fasync->poll = poll;
list_move(&fasync->list, &snd_fasync_list);
schedule_work(&snd_fasync_work);
spin_unlock_irqrestore(&snd_fasync_lock, flags);
}
EXPORT_SYMBOL_GPL(snd_kill_fasync);
void snd_fasync_free(struct snd_fasync *fasync)
{
if (!fasync)
return;
fasync->on = 0;
flush_work(&snd_fasync_work);
kfree(fasync);
}
EXPORT_SYMBOL_GPL(snd_fasync_free);