splat: Fix log buffer locking

The Fedora 3.6 debug kernel identified the following issue where
we call copy_to_user() under a spin lock().  This used to be safe
in older kernels but no longer appears to be true so the spin
lock was changed to a mutex.  None of this code is performance
critical so allowing the process to sleep is harmless.

Signed-off-by: Brian Behlendorf <[email protected]>

2 files changed, 15 insertions, 14 deletions

diff --git a/module/splat/splat-ctl.c b/module/splat/splat-ctl.c
index 53bf51dd6..c68281a84 100644
--- a/module/splat/splat-ctl.c
+++ b/module/splat/splat-ctl.c
@@ -71,7 +71,7 @@ splat_open(struct inode *inode, struct file *file)
 	if (info == NULL)
 		return -ENOMEM;
 
-	spin_lock_init(&info->info_lock);
+	mutex_init(&info->info_lock);
 	info->info_size = SPLAT_INFO_BUFFER_SIZE;
 	info->info_buffer = (char *)vmalloc(SPLAT_INFO_BUFFER_SIZE);
 	if (info->info_buffer == NULL) {
@@ -100,6 +100,7 @@ splat_release(struct inode *inode, struct file *file)
 	ASSERT(info);
 	ASSERT(info->info_buffer);
 
+	mutex_destroy(&info->info_lock);
 	vfree(info->info_buffer);
 	kfree(info);
 
@@ -114,10 +115,10 @@ splat_buffer_clear(struct file *file, splat_cfg_t *kcfg, unsigned long arg)
 	ASSERT(info);
 	ASSERT(info->info_buffer);
 
-	spin_lock(&info->info_lock);
+	mutex_lock(&info->info_lock);
 	memset(info->info_buffer, 0, info->info_size);
 	info->info_head = info->info_buffer;
-	spin_unlock(&info->info_lock);
+	mutex_unlock(&info->info_lock);
 
 	return 0;
 }
@@ -132,7 +133,7 @@ splat_buffer_size(struct file *file, splat_cfg_t *kcfg, unsigned long arg)
 	ASSERT(info);
 	ASSERT(info->info_buffer);
 
-	spin_lock(&info->info_lock);
+	mutex_lock(&info->info_lock);
 	if (kcfg->cfg_arg1 > 0) {
 
 		size = kcfg->cfg_arg1;
@@ -157,7 +158,7 @@ splat_buffer_size(struct file *file, splat_cfg_t *kcfg, unsigned long arg)
 	if (copy_to_user((struct splat_cfg_t __user *)arg, kcfg, sizeof(*kcfg)))
 		rc = -EFAULT;
 out:
-	spin_unlock(&info->info_lock);
+	mutex_unlock(&info->info_lock);
 
 	return rc;
 }
@@ -508,7 +509,7 @@ static ssize_t splat_write(struct file *file, const char __user *buf,
 	ASSERT(info);
 	ASSERT(info->info_buffer);
 
-	spin_lock(&info->info_lock);
+	mutex_lock(&info->info_lock);
 
 	/* Write beyond EOF */
 	if (*ppos >= info->info_size) {
@@ -528,7 +529,7 @@ static ssize_t splat_write(struct file *file, const char __user *buf,
 	*ppos += count;
 	rc = count;
 out:
-	spin_unlock(&info->info_lock);
+	mutex_unlock(&info->info_lock);
 	return rc;
 }
 
@@ -545,7 +546,7 @@ static ssize_t splat_read(struct file *file, char __user *buf,
 	ASSERT(info);
 	ASSERT(info->info_buffer);
 
-	spin_lock(&info->info_lock);
+	mutex_lock(&info->info_lock);
 
 	/* Read beyond EOF */
 	if (*ppos >= info->info_size)
@@ -563,7 +564,7 @@ static ssize_t splat_read(struct file *file, char __user *buf,
 	*ppos += count;
 	rc = count;
 out:
-	spin_unlock(&info->info_lock);
+	mutex_unlock(&info->info_lock);
 	return rc;
 }
 
@@ -579,7 +580,7 @@ static loff_t splat_seek(struct file *file, loff_t offset, int origin)
 	ASSERT(info);
 	ASSERT(info->info_buffer);
 
-	spin_lock(&info->info_lock);
+	mutex_lock(&info->info_lock);
 
 	switch (origin) {
 	case 0: /* SEEK_SET - No-op just do it */
@@ -598,7 +599,7 @@ static loff_t splat_seek(struct file *file, loff_t offset, int origin)
 		rc = offset;
 	}
 
-	spin_unlock(&info->info_lock);
+	mutex_unlock(&info->info_lock);
 
 	return rc;
 }
diff --git a/module/splat/splat-internal.h b/module/splat/splat-internal.h
index b15db65e2..14303a105 100644
--- a/module/splat/splat-internal.h
+++ b/module/splat/splat-internal.h
@@ -121,7 +121,7 @@ typedef struct splat_subsystem {
 #define SPLAT_INFO_BUFFER_REDZONE	256
 
 typedef struct splat_info {
-	spinlock_t info_lock;
+	struct mutex info_lock;
 	int info_size;
 	char *info_buffer;
 	char *info_head;	/* Internal kernel use only */
@@ -136,7 +136,7 @@ typedef struct splat_info {
 	ASSERT(_info_);							\
 	ASSERT(_info_->info_buffer);					\
 									\
-	spin_lock(&_info_->info_lock);					\
+	mutex_lock(&_info_->info_lock);					\
 									\
 	/* Don't allow the kernel to start a write in the red zone */	\
 	if ((int)(_info_->info_head - _info_->info_buffer) >		\
@@ -148,7 +148,7 @@ typedef struct splat_info {
 			_info_->info_head += _rc_;			\
 	}								\
 									\
-	spin_unlock(&_info_->info_lock);				\
+	mutex_unlock(&_info_->info_lock);				\
 	_rc_;								\
 })