[PATCH -mm] updated idetape gcc 4.1 warning fix

[PATCH -mm] updated idetape gcc 4.1 warning fix

[Daniel Walker]

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I added returns for failures .. I would hope that this doesn't break anything in
userspace , but I'll confess that I have no way to determin that for certain . 

Hows that Alan?

Fixes the following warning,

drivers/ide/ide-tape.c: In function ‘idetape_copy_stage_from_user’:
drivers/ide/ide-tape.c:2662: warning: ignoring return value of ‘copy_from_user’, declared with attribute warn_unused_result
drivers/ide/ide-tape.c: In function ‘idetape_copy_stage_to_user’:
drivers/ide/ide-tape.c:2689: warning: ignoring return value of ‘copy_to_user’, declared with attribute warn_unused_result

Signed-Off-By: Daniel Walker <dwalker@mvista.com>

Index: linux-2.6.16/drivers/ide/ide-tape.c
===================================================================
--- linux-2.6.16.orig/drivers/ide/ide-tape.c
+++ linux-2.6.16/drivers/ide/ide-tape.c
@@ -2645,7 +2645,7 @@ static idetape_stage_t *idetape_kmalloc_
 	return __idetape_kmalloc_stage(tape, 0, 0);
 }
 
-static void idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
+static int idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
 {
 	struct idetape_bh *bh = tape->bh;
 	int count;
@@ -2655,11 +2655,12 @@ static void idetape_copy_stage_from_user
 		if (bh == NULL) {
 			printk(KERN_ERR "ide-tape: bh == NULL in "
 				"idetape_copy_stage_from_user\n");
-			return;
+			return 1;
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), (unsigned int)n);
-		copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count);
+		if (copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count))
+			return 1;
 		n -= count;
 		atomic_add(count, &bh->b_count);
 		buf += count;
@@ -2670,9 +2671,10 @@ static void idetape_copy_stage_from_user
 		}
 	}
 	tape->bh = bh;
+	return 0;
 }
 
-static void idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
+static int idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
 {
 	struct idetape_bh *bh = tape->bh;
 	int count;
@@ -2682,11 +2684,12 @@ static void idetape_copy_stage_to_user (
 		if (bh == NULL) {
 			printk(KERN_ERR "ide-tape: bh == NULL in "
 				"idetape_copy_stage_to_user\n");
-			return;
+			return 1;
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		count = min(tape->b_count, n);
-		copy_to_user(buf, tape->b_data, count);
+		if  (copy_to_user(buf, tape->b_data, count))
+			return 1;
 		n -= count;
 		tape->b_data += count;
 		tape->b_count -= count;
@@ -2699,6 +2702,7 @@ static void idetape_copy_stage_to_user (
 			}
 		}
 	}
+	return 0;
 }
 
 static void idetape_init_merge_stage (idetape_tape_t *tape)
@@ -3736,7 +3740,8 @@ static ssize_t idetape_chrdev_read (stru
 		return (0);
 	if (tape->merge_stage_size) {
 		actually_read = min((unsigned int)(tape->merge_stage_size), (unsigned int)count);
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read))
+			return -EFAULT;
 		buf += actually_read;
 		tape->merge_stage_size -= actually_read;
 		count -= actually_read;
@@ -3745,7 +3750,8 @@ static ssize_t idetape_chrdev_read (stru
 		bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
 		if (bytes_read <= 0)
 			goto finish;
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read))
+			return -EFAULT;
 		buf += bytes_read;
 		count -= bytes_read;
 		actually_read += bytes_read;
@@ -3755,7 +3761,8 @@ static ssize_t idetape_chrdev_read (stru
 		if (bytes_read <= 0)
 			goto finish;
 		temp = min((unsigned long)count, (unsigned long)bytes_read);
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp))
+			return -EFAULT;
 		actually_read += temp;
 		tape->merge_stage_size = bytes_read-temp;
 	}
@@ -3833,7 +3840,8 @@ static ssize_t idetape_chrdev_write (str
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		actually_written = min((unsigned int)(tape->stage_size - tape->merge_stage_size), (unsigned int)count);
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written))
+				return -EFAULT;
 		buf += actually_written;
 		tape->merge_stage_size += actually_written;
 		count -= actually_written;
@@ -3846,7 +3854,8 @@ static ssize_t idetape_chrdev_write (str
 		}
 	}
 	while (count >= tape->stage_size) {
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size))
+			return -EFAULT;
 		buf += tape->stage_size;
 		count -= tape->stage_size;
 		retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
@@ -3856,7 +3865,8 @@ static ssize_t idetape_chrdev_write (str
 	}
 	if (count) {
 		actually_written += count;
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count))
+			return -EFAULT;
 		tape->merge_stage_size += count;
 	}
 	return (actually_written);

Re: [PATCH -mm] updated idetape gcc 4.1 warning fix

[Alan Cox]

On Mer, 2006-05-10 at 11:10 -0700, Daniel Walker wrote:
> I added returns for failures .. I would hope that this doesn't break anything in
> userspace , but I'll confess that I have no way to determin that for certain . 
> 
> Hows that Alan?

You still need to walk the BHs I think. Also if an error occurs and some
data is successfully transferred the standards explicitly require you
return the amount of data successfully transferred if you report an
error.

Re: [PATCH -mm] updated idetape gcc 4.1 warning fix

[Daniel Walker]

On Thu, 2006-05-11 at 14:11 +0100, Alan Cox wrote:
> On Mer, 2006-05-10 at 11:10 -0700, Daniel Walker wrote:
> > I added returns for failures .. I would hope that this doesn't break anything in
> > userspace , but I'll confess that I have no way to determin that for certain . 
> > 
> > Hows that Alan?
> 
> You still need to walk the BHs I think. Also if an error occurs and some
> data is successfully transferred the standards explicitly require you
> return the amount of data successfully transferred if you report an
> error.


So it should try to write something even on an error ? It looks like it
would be really difficult to drop the data off the BHs without actually
doing the write .. The most straight forward way to handle the error
would be write all the data copied ..

Daniel

Re: [PATCH -mm] updated idetape gcc 4.1 warning fix

[Alan Cox]

On Iau, 2006-05-11 at 10:14 -0700, Daniel Walker wrote:
> So it should try to write something even on an error ? It looks like it
> would be really difficult to drop the data off the BHs without actually
> doing the write .. The most straight forward way to handle the error
> would be write all the data copied ..

copy_from_user zero fills failure space so that bit is an accounting job
only. 

[PATCH -mm] updated idetape gcc 4.1 warning fix

[Daniel Walker]

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Another idetape fixup attempt.

In both the read and write cases it will return an error if copy_{from/to}_user
faults. However, I let the driver try to read/write as much as it can just
as it normally would , then finally it returns an error if there was one.
This was the most straight forward way to handle the error , since there
isn't a clear way to clean up the buffers on error .

I moved retval in idetape_chrdev_write() down into the actual code blocks
since it's really once used there, and it conflicted with my ret variable. 

Fixes the following warning,

drivers/ide/ide-tape.c: In function ‘idetape_copy_stage_from_user’:
drivers/ide/ide-tape.c:2662: warning: ignoring return value of ‘copy_from_user’, declared with attribute warn_unused_result
drivers/ide/ide-tape.c: In function ‘idetape_copy_stage_to_user’:
drivers/ide/ide-tape.c:2689: warning: ignoring return value of ‘copy_to_user’, declared with attribute warn_unused_result

Signed-Off-By: Daniel Walker <dwalker@mvista.com>

Index: linux-2.6.16/drivers/ide/ide-tape.c
===================================================================
--- linux-2.6.16.orig/drivers/ide/ide-tape.c
+++ linux-2.6.16/drivers/ide/ide-tape.c
@@ -2646,21 +2646,23 @@ static idetape_stage_t *idetape_kmalloc_
 	return __idetape_kmalloc_stage(tape, 0, 0);
 }
 
-static void idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
+static int idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
 {
 	struct idetape_bh *bh = tape->bh;
 	int count;
+	int ret = 0;
 
 	while (n) {
 #if IDETAPE_DEBUG_BUGS
 		if (bh == NULL) {
 			printk(KERN_ERR "ide-tape: bh == NULL in "
 				"idetape_copy_stage_from_user\n");
-			return;
+			return 1;
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), (unsigned int)n);
-		copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count);
+		if (copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count))
+			ret = 1;
 		n -= count;
 		atomic_add(count, &bh->b_count);
 		buf += count;
@@ -2671,23 +2673,26 @@ static void idetape_copy_stage_from_user
 		}
 	}
 	tape->bh = bh;
+	return ret;
 }
 
-static void idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
+static int idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
 {
 	struct idetape_bh *bh = tape->bh;
 	int count;
+	int ret = 0;
 
 	while (n) {
 #if IDETAPE_DEBUG_BUGS
 		if (bh == NULL) {
 			printk(KERN_ERR "ide-tape: bh == NULL in "
 				"idetape_copy_stage_to_user\n");
-			return;
+			return 1;
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		count = min(tape->b_count, n);
-		copy_to_user(buf, tape->b_data, count);
+		if  (copy_to_user(buf, tape->b_data, count))
+			ret = 1;
 		n -= count;
 		tape->b_data += count;
 		tape->b_count -= count;
@@ -2700,6 +2705,7 @@ static void idetape_copy_stage_to_user (
 			}
 		}
 	}
+	return ret;
 }
 
 static void idetape_init_merge_stage (idetape_tape_t *tape)
@@ -3719,6 +3725,7 @@ static ssize_t idetape_chrdev_read (stru
 	struct ide_tape_obj *tape = ide_tape_f(file);
 	ide_drive_t *drive = tape->drive;
 	ssize_t bytes_read,temp, actually_read = 0, rc;
+	ssize_t ret = 0;
 
 #if IDETAPE_DEBUG_LOG
 	if (tape->debug_level >= 3)
@@ -3737,7 +3744,8 @@ static ssize_t idetape_chrdev_read (stru
 		return (0);
 	if (tape->merge_stage_size) {
 		actually_read = min((unsigned int)(tape->merge_stage_size), (unsigned int)count);
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read))
+			ret = -EFAULT;
 		buf += actually_read;
 		tape->merge_stage_size -= actually_read;
 		count -= actually_read;
@@ -3746,7 +3754,8 @@ static ssize_t idetape_chrdev_read (stru
 		bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
 		if (bytes_read <= 0)
 			goto finish;
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read))
+			ret = -EFAULT;
 		buf += bytes_read;
 		count -= bytes_read;
 		actually_read += bytes_read;
@@ -3756,7 +3765,8 @@ static ssize_t idetape_chrdev_read (stru
 		if (bytes_read <= 0)
 			goto finish;
 		temp = min((unsigned long)count, (unsigned long)bytes_read);
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp))
+			ret = -EFAULT;
 		actually_read += temp;
 		tape->merge_stage_size = bytes_read-temp;
 	}
@@ -3769,7 +3779,8 @@ finish:
 		idetape_space_over_filemarks(drive, MTFSF, 1);
 		return 0;
 	}
-	return actually_read;
+
+	return (ret) ? ret : actually_read;
 }
 
 static ssize_t idetape_chrdev_write (struct file *file, const char __user *buf,
@@ -3777,7 +3788,8 @@ static ssize_t idetape_chrdev_write (str
 {
 	struct ide_tape_obj *tape = ide_tape_f(file);
 	ide_drive_t *drive = tape->drive;
-	ssize_t retval, actually_written = 0;
+	ssize_t actually_written = 0;
+	ssize_t ret = 0;
 
 	/* The drive is write protected. */
 	if (tape->write_prot)
@@ -3813,7 +3825,7 @@ static ssize_t idetape_chrdev_write (str
 		 *	some drives (Seagate STT3401A) will return an error.
 		 */
 		if (drive->dsc_overlap) {
-			retval = idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, 0, tape->merge_stage->bh);
+			ssize_t retval = idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, 0, tape->merge_stage->bh);
 			if (retval < 0) {
 				__idetape_kfree_stage(tape->merge_stage);
 				tape->merge_stage = NULL;
@@ -3834,12 +3846,14 @@ static ssize_t idetape_chrdev_write (str
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		actually_written = min((unsigned int)(tape->stage_size - tape->merge_stage_size), (unsigned int)count);
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written))
+				ret = -EFAULT;
 		buf += actually_written;
 		tape->merge_stage_size += actually_written;
 		count -= actually_written;
 
 		if (tape->merge_stage_size == tape->stage_size) {
+			ssize_t retval;
 			tape->merge_stage_size = 0;
 			retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
 			if (retval <= 0)
@@ -3847,7 +3861,9 @@ static ssize_t idetape_chrdev_write (str
 		}
 	}
 	while (count >= tape->stage_size) {
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size);
+		ssize_t retval;
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size))
+			ret = -EFAULT;
 		buf += tape->stage_size;
 		count -= tape->stage_size;
 		retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
@@ -3857,10 +3873,11 @@ static ssize_t idetape_chrdev_write (str
 	}
 	if (count) {
 		actually_written += count;
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count))
+			ret = -EFAULT;
 		tape->merge_stage_size += count;
 	}
-	return (actually_written);
+	return (ret) ? ret : actually_written;
 }
 
 static int idetape_write_filemark (ide_drive_t *drive)

Re: [PATCH -mm] updated idetape gcc 4.1 warning fix

[Jesper Juhl]

On 5/10/06, Daniel Walker <dwalker@mvista.com> wrote:
> I added returns for failures .. I would hope that this doesn't break anything in
> userspace , but I'll confess that I have no way to determin that for certain .
>
> Hows that Alan?
>
> Fixes the following warning,
>
> drivers/ide/ide-tape.c: In function 'idetape_copy_stage_from_user':
> drivers/ide/ide-tape.c:2662: warning: ignoring return value of 'copy_from_user', declared with attribute warn_unused_result
> drivers/ide/ide-tape.c: In function 'idetape_copy_stage_to_user':
> drivers/ide/ide-tape.c:2689: warning: ignoring return value of 'copy_to_user', declared with attribute warn_unused_result
>

I've been down the road of trying to fix that code as well a while back.
Although my patches had flaws and didn't go in, perhaps your current
attempt could bennefit by looking at what I tried to do back then and
the feedback I recieved, so I thought I'd point them out to you.

Take a look at the two threads named "[PATCH] ide-tape: attempt to
handle copy_*_user() failures" and "[PATCH] ide-tape: attempt to
handle copy_*_user() failures [take two]"

Here's a link to them in the archives :
http://marc.theaimsgroup.com/?t=113796611500003&r=1&w=2


-- 
Jesper Juhl <jesper.juhl@gmail.com>
Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please      http://www.expita.com/nomime.html

[PATCH -mm] updated idetape gcc 4.1 warning fix

[Daniel Walker]

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I added returns for failures .. I would hope that this doesn't break anything in
userspace , but I'll confess that I have no way to determin that for certain . 

Hows that Alan?

Fixes the following warning,

drivers/ide/ide-tape.c: In function ‘idetape_copy_stage_from_user’:
drivers/ide/ide-tape.c:2662: warning: ignoring return value of ‘copy_from_user’, declared with attribute warn_unused_result
drivers/ide/ide-tape.c: In function ‘idetape_copy_stage_to_user’:
drivers/ide/ide-tape.c:2689: warning: ignoring return value of ‘copy_to_user’, declared with attribute warn_unused_result

Signed-Off-By: Daniel Walker <dwalker@mvista.com>

Index: linux-2.6.16/drivers/ide/ide-tape.c
===================================================================
--- linux-2.6.16.orig/drivers/ide/ide-tape.c
+++ linux-2.6.16/drivers/ide/ide-tape.c
@@ -2645,7 +2645,7 @@ static idetape_stage_t *idetape_kmalloc_
 	return __idetape_kmalloc_stage(tape, 0, 0);
 }
 
-static void idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
+static int idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
 {
 	struct idetape_bh *bh = tape->bh;
 	int count;
@@ -2655,11 +2655,12 @@ static void idetape_copy_stage_from_user
 		if (bh == NULL) {
 			printk(KERN_ERR "ide-tape: bh == NULL in "
 				"idetape_copy_stage_from_user\n");
-			return;
+			return 1;
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), (unsigned int)n);
-		copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count);
+		if (copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count))
+			return 1;
 		n -= count;
 		atomic_add(count, &bh->b_count);
 		buf += count;
@@ -2670,9 +2671,10 @@ static void idetape_copy_stage_from_user
 		}
 	}
 	tape->bh = bh;
+	return 0;
 }
 
-static void idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
+static int idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
 {
 	struct idetape_bh *bh = tape->bh;
 	int count;
@@ -2682,11 +2684,12 @@ static void idetape_copy_stage_to_user (
 		if (bh == NULL) {
 			printk(KERN_ERR "ide-tape: bh == NULL in "
 				"idetape_copy_stage_to_user\n");
-			return;
+			return 1;
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		count = min(tape->b_count, n);
-		copy_to_user(buf, tape->b_data, count);
+		if  (copy_to_user(buf, tape->b_data, count))
+			return 1;
 		n -= count;
 		tape->b_data += count;
 		tape->b_count -= count;
@@ -2699,6 +2702,7 @@ static void idetape_copy_stage_to_user (
 			}
 		}
 	}
+	return 0;
 }
 
 static void idetape_init_merge_stage (idetape_tape_t *tape)
@@ -3736,7 +3740,8 @@ static ssize_t idetape_chrdev_read (stru
 		return (0);
 	if (tape->merge_stage_size) {
 		actually_read = min((unsigned int)(tape->merge_stage_size), (unsigned int)count);
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read))
+			return -EFAULT;
 		buf += actually_read;
 		tape->merge_stage_size -= actually_read;
 		count -= actually_read;
@@ -3745,7 +3750,8 @@ static ssize_t idetape_chrdev_read (stru
 		bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
 		if (bytes_read <= 0)
 			goto finish;
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read))
+			return -EFAULT;
 		buf += bytes_read;
 		count -= bytes_read;
 		actually_read += bytes_read;
@@ -3755,7 +3761,8 @@ static ssize_t idetape_chrdev_read (stru
 		if (bytes_read <= 0)
 			goto finish;
 		temp = min((unsigned long)count, (unsigned long)bytes_read);
-		idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp);
+		if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp))
+			return -EFAULT;
 		actually_read += temp;
 		tape->merge_stage_size = bytes_read-temp;
 	}
@@ -3833,7 +3840,8 @@ static ssize_t idetape_chrdev_write (str
 		}
 #endif /* IDETAPE_DEBUG_BUGS */
 		actually_written = min((unsigned int)(tape->stage_size - tape->merge_stage_size), (unsigned int)count);
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written))
+				return -EFAULT;
 		buf += actually_written;
 		tape->merge_stage_size += actually_written;
 		count -= actually_written;
@@ -3846,7 +3854,8 @@ static ssize_t idetape_chrdev_write (str
 		}
 	}
 	while (count >= tape->stage_size) {
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size))
+			return -EFAULT;
 		buf += tape->stage_size;
 		count -= tape->stage_size;
 		retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
@@ -3856,7 +3865,8 @@ static ssize_t idetape_chrdev_write (str
 	}
 	if (count) {
 		actually_written += count;
-		idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count);
+		if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count))
+			return -EFAULT;
 		tape->merge_stage_size += count;
 	}
 	return (actually_written);