[alsa-devel] [PATCH v3] ALSA: timer: fix gparams ioctl compatibility for different architectures

[Takashi Sakamoto]

'struct snd_timer_gparams' includes some members with 'unsigned long',
therefore its size differs depending on data models of architecture. As
a result, x86/x32 applications fail to execute ioctl(2) with
SNDRV_TIMER_GPARAMS command on x86_64 machine.

This commit fixes this bug by adding a pair of structure and ioctl
command for the compatibility.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 sound/core/timer.c        | 20 +++++++++++++-------
 sound/core/timer_compat.c | 30 +++++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index aa1b15c..ea4d999 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -1502,17 +1502,13 @@ static int snd_timer_user_ginfo(struct file *file,
 	return err;
 }
 
-static int snd_timer_user_gparams(struct file *file,
-				  struct snd_timer_gparams __user *_gparams)
+static int timer_set_gparams(struct snd_timer_gparams *gparams)
 {
-	struct snd_timer_gparams gparams;
 	struct snd_timer *t;
 	int err;
 
-	if (copy_from_user(&gparams, _gparams, sizeof(gparams)))
-		return -EFAULT;
 	mutex_lock(&register_mutex);
-	t = snd_timer_find(&gparams.tid);
+	t = snd_timer_find(&gparams->tid);
 	if (!t) {
 		err = -ENODEV;
 		goto _error;
@@ -1525,12 +1521,22 @@ static int snd_timer_user_gparams(struct file *file,
 		err = -ENOSYS;
 		goto _error;
 	}
-	err = t->hw.set_period(t, gparams.period_num, gparams.period_den);
+	err = t->hw.set_period(t, gparams->period_num, gparams->period_den);
 _error:
 	mutex_unlock(&register_mutex);
 	return err;
 }
 
+static int snd_timer_user_gparams(struct file *file,
+				  struct snd_timer_gparams __user *_gparams)
+{
+	struct snd_timer_gparams gparams;
+
+	if (copy_from_user(&gparams, _gparams, sizeof(gparams)))
+		return -EFAULT;
+	return timer_set_gparams(&gparams);
+}
+
 static int snd_timer_user_gstatus(struct file *file,
 				  struct snd_timer_gstatus __user *_gstatus)
 {
diff --git a/sound/core/timer_compat.c b/sound/core/timer_compat.c
index 2e90822..6a437eb 100644
--- a/sound/core/timer_compat.c
+++ b/sound/core/timer_compat.c
@@ -22,6 +22,19 @@
 
 #include <linux/compat.h>
 
+/*
+ * ILP32/LP64 has different size for 'long' type. Additionally, the size
+ * of storage alignment differs depending on architectures. Here, '__packed'
+ * qualifier is used so that the size of this structure is multiple of 4 and
+ * it fits to any architectures with 32 bit storage alignment.
+ */
+struct snd_timer_gparams32 {
+	struct snd_timer_id tid;
+	u32 period_num;
+	u32 period_den;
+	unsigned char reserved[32];
+} __packed;
+
 struct snd_timer_info32 {
 	u32 flags;
 	s32 card;
@@ -32,6 +45,19 @@ struct snd_timer_info32 {
 	unsigned char reserved[64];
 };
 
+static int snd_timer_user_gparams_compat(struct file *file,
+					struct snd_timer_gparams32 __user *user)
+{
+	struct snd_timer_gparams gparams;
+
+	if (copy_from_user(&gparams.tid, &user->tid, sizeof(gparams.tid)) ||
+	    get_user(gparams.period_num, &user->period_num) ||
+	    get_user(gparams.period_den, &user->period_den))
+		return -EFAULT;
+
+	return timer_set_gparams(&gparams);
+}
+
 static int snd_timer_user_info_compat(struct file *file,
 				      struct snd_timer_info32 __user *_info)
 {
@@ -99,6 +125,7 @@ static int snd_timer_user_status_compat(struct file *file,
  */
 
 enum {
+	SNDRV_TIMER_IOCTL_GPARAMS32 = _IOW('T', 0x04, struct snd_timer_gparams32),
 	SNDRV_TIMER_IOCTL_INFO32 = _IOR('T', 0x11, struct snd_timer_info32),
 	SNDRV_TIMER_IOCTL_STATUS32 = _IOW('T', 0x14, struct snd_timer_status32),
 #ifdef CONFIG_X86_X32
@@ -114,7 +141,6 @@ static long snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, uns
 	case SNDRV_TIMER_IOCTL_PVERSION:
 	case SNDRV_TIMER_IOCTL_TREAD:
 	case SNDRV_TIMER_IOCTL_GINFO:
-	case SNDRV_TIMER_IOCTL_GPARAMS:
 	case SNDRV_TIMER_IOCTL_GSTATUS:
 	case SNDRV_TIMER_IOCTL_SELECT:
 	case SNDRV_TIMER_IOCTL_PARAMS:
@@ -128,6 +154,8 @@ static long snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, uns
 	case SNDRV_TIMER_IOCTL_PAUSE_OLD:
 	case SNDRV_TIMER_IOCTL_NEXT_DEVICE:
 		return snd_timer_user_ioctl(file, cmd, (unsigned long)argp);
+	case SNDRV_TIMER_IOCTL_GPARAMS32:
+		return snd_timer_user_gparams_compat(file, argp);
 	case SNDRV_TIMER_IOCTL_INFO32:
 		return snd_timer_user_info_compat(file, argp);
 	case SNDRV_TIMER_IOCTL_STATUS32:
-- 
2.7.3