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goldfish: locking bugs in goldfish_pipe_read_write()

PATCH In review Dan Carpenter 2 participants 2 messages Feb 2, 2016 Kernel janitors

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Dan Carpenter

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#0 lore raw

PATCH 1/1 goldfish: locking bugs in goldfish_pipe_read_write()

We recently messed up the error handling here. We can return with the pipe->lock held or sometimes we unlock twice by mistake.

Fixes 2f3be88237a3 ('goldfish_pipe: Pin pages to memory while copying and other cleanups')
Signed-off-by Dan Carpenter <[email protected]>
drivers/platform/goldfish/goldfish_pipe.c +8 -14
index e3fab9a..839df4a 100644
@@ -313,7 +313,7 @@ static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
 				     !is_write, 0, &page, NULL);
 		up_read(&current->mm->mmap_sem);
 		if (ret < 0)
-			return ret;
+			break;
 
 		if (dev->version) {
 			/* Device version 1 or newer (qemu-android) expects the

@@ -400,22 +400,16 @@ static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
 		while (test_bit(wakeBit, &pipe->flags)) {
 			if (wait_event_interruptible(
 					pipe->wake_queue,
-					!test_bit(wakeBit, &pipe->flags))) {
-				ret = -ERESTARTSYS;
-				break;
-			}
-
-			if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags)) {
-				ret = -EIO;
-				break;
-			}
+					!test_bit(wakeBit, &pipe->flags)))
+				return -ERESTARTSYS;
+
+			if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
+				return -EIO;
 		}
 
 		/* Try to re-acquire the lock */
-		if (mutex_lock_interruptible(&pipe->lock)) {
-			ret = -ERESTARTSYS;
-			break;
-		}
+		if (mutex_lock_interruptible(&pipe->lock))
+			return -ERESTARTSYS;
 	}
 	mutex_unlock(&pipe->lock);
Reviewed-by on v1 1/1
#1 lore raw
Quoted 39 lines · Dan Carpenter

We recently messed up the error handling here. We can return with the pipe->lock held or sometimes we unlock twice by mistake.

Fixes 2f3be88237a3 ('goldfish_pipe: Pin pages to memory while copying and other cleanups')
Signed-off-by Dan Carpenter <[email protected]>
drivers/platform/goldfish/goldfish_pipe.c +6 -10
index e3fab9a..839df4a 100644
@@ -313,7 +313,7 @@ static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
 				     !is_write, 0, &page, NULL);
 		up_read(&current->mm->mmap_sem);
 		if (ret < 0)
-			return ret;
+			break;
 
 		if (dev->version) {
 			/* Device version 1 or newer (qemu-android) expects the

@@ -400,22 +400,16 @@ static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
 		while (test_bit(wakeBit, &pipe->flags)) {
 			if (wait_event_interruptible(
 					pipe->wake_queue,
-					!test_bit(wakeBit, &pipe->flags))) {
-				ret = -ERESTARTSYS;
-				break;
-			}
-
-			if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags)) {
-				ret = -EIO;
-				break;
-			}
+					!test_bit(wakeBit, &pipe->flags)))
+				return -ERESTARTSYS;
+
+			if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
+				return -EIO;
 		}

drivers/platform/goldfish/goldfish_pipe.c static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer, · line 415

Quoted 10 lines
drivers/platform/goldfish/goldfish_pipe.c +2 -4
 		/* Try to re-acquire the lock */
-		if (mutex_lock_interruptible(&pipe->lock)) {
-			ret = -ERESTARTSYS;
-			break;
-		}
+		if (mutex_lock_interruptible(&pipe->lock))
+			return -ERESTARTSYS;
 	}
 	mutex_unlock(&pipe->lock);

yeah, that was pretty broken, thanks for fixing this.

Reviewed-by Christoffer Dall <[email protected]>