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pipewire-v4l2: only access globals.fd_maps while holding globals.lock

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`fd_map` structures are allocated in a `pw_array`. When inserting into
a full `pw_array`, it is resized to accomodate the new elements. In that case,
all `fd_map` pointers may be invalidated. Hence it is only safe to access
`fd_map` structs while holding `globals.lock`, which prevents any modifications
to the fd map array, thus keeping the references valid.
This commit is contained in:
Barnabás Pőcze 2021-10-14 20:57:23 +02:00 committed by Wim Taymans
parent e1898812b2
commit 5e1a93d61d
1 changed files with 40 additions and 27 deletions
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67
pipewire-v4l2/src/pipewire-v4l2.c
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@ -299,37 +299,55 @@ static int add_fd_map(int fd, struct file *file)
pthread_mutex_unlock(&globals.lock);
return 0;
}
static struct fd_map *find_fd_map(int fd)
/* must be called with `globals.lock` held */
static struct fd_map *find_fd_map_unlocked(int fd)
{
struct fd_map *map, *res = NULL;
pthread_mutex_lock(&globals.lock);
struct fd_map *map;
pw_array_for_each(map, &globals.fd_maps) {
if (map->fd == fd) {
ATOMIC_INC(map->file->ref);
res = map;
break;
return map;
}
}
pthread_mutex_unlock(&globals.lock);
return res;
return NULL;
}
static struct file *find_file(int fd)
{
struct fd_map *map = find_fd_map(fd);
if (map == NULL)
return NULL;
return map->file;
}
static void remove_fd_map(struct fd_map *map)
{
struct file *file = map->file;
pthread_mutex_lock(&globals.lock);
pw_array_remove(&globals.fd_maps, map);
struct fd_map *map = find_fd_map_unlocked(fd);
struct file *file = NULL;
if (map != NULL)
file = map->file;
pthread_mutex_unlock(&globals.lock);
unref_file(file);
return file;
}
static struct file *remove_fd_map(int fd)
{
pthread_mutex_lock(&globals.lock);
struct fd_map *map = find_fd_map_unlocked(fd);
struct file *file = NULL;
if (map != NULL) {
file = map->file;
pw_array_remove(&globals.fd_maps, map);
}
pthread_mutex_unlock(&globals.lock);
if (file != NULL)
unref_file(file);
return file;
}
static int add_file_map(void *addr, struct file *file)
@ -711,20 +729,15 @@ static int v4l2_dup(int oldfd)
static int v4l2_close(int fd)
{
int res = 0;
struct file *file;
struct fd_map *map;
struct file *file = remove_fd_map(fd);
if ((map = find_fd_map(fd)) == NULL)
if (file == NULL)
return globals.old_fops.close(fd);
file = map->file;
remove_fd_map(map);
unref_file(file);
pw_log_info("fd:%d -> %d (%s)", fd,
res, strerror(res < 0 ? errno : 0));
return res;
pw_log_info("fd:%d closed", fd);
return 0;
}
#define KERNEL_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + (c))