[PATCH] fsi: fix bogos error returns from cfam_read and cfam_write

[PATCH] fsi: fix bogos error returns from cfam_read and cfam_write

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

In the case where errors occur in functions cfam_read and cfam_write
the error return code in rc is not returned and a bogus non-error
count size is returned instead. Fix this by returning the correct
error code when an error occurs or the count size if the functions
worked correctly.

Addresses-Coverity: ("Unused value")
Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/fsi/fsi-core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 8244da8a7241..c3885b138ead 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -718,7 +718,7 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
 	rc = count;
  fail:
 	*offset = off;
-	return count;
+	return rc;
 }
 
 static ssize_t cfam_write(struct file *filep, const char __user *buf,
@@ -755,7 +755,7 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
 	rc = count;
  fail:
 	*offset = off;
-	return count;
+	return rc;
 }
 
 static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
-- 
2.24.0

Re: [PATCH] fsi: fix bogos error returns from cfam_read and cfam_write

[Andrew Jeffery]

On Sat, 23 Nov 2019, at 10:01, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> In the case where errors occur in functions cfam_read and cfam_write
> the error return code in rc is not returned and a bogus non-error
> count size is returned instead. Fix this by returning the correct
> error code when an error occurs or the count size if the functions
> worked correctly.
> 
> Addresses-Coverity: ("Unused value")
> Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Reviewed-by: Andrew Jeffery <andrew@aj.id.au>

Re: [PATCH] fsi: fix bogos error returns from cfam_read and cfam_write

[Joel Stanley]

Hi Colin,

On Fri, 22 Nov 2019 at 23:31, Colin King <colin.king@canonical.com> wrote:
>
> From: Colin Ian King <colin.king@canonical.com>
>
> In the case where errors occur in functions cfam_read and cfam_write
> the error return code in rc is not returned and a bogus non-error
> count size is returned instead. Fix this by returning the correct
> error code when an error occurs or the count size if the functions
> worked correctly.

 You're correct that if there's an error we need to return an error.

However the other case is when there's a partial read that completed.
We already advance the file offset, but I think we should also return
the number of bytes successfully read.

Cheers,

Joel

>
> Addresses-Coverity: ("Unused value")
> Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/fsi/fsi-core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
> index 8244da8a7241..c3885b138ead 100644
> --- a/drivers/fsi/fsi-core.c
> +++ b/drivers/fsi/fsi-core.c
> @@ -718,7 +718,7 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
>         rc = count;
>   fail:
>         *offset = off;
> -       return count;
> +       return rc;
>  }
>
>  static ssize_t cfam_write(struct file *filep, const char __user *buf,
> @@ -755,7 +755,7 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
>         rc = count;
>   fail:
>         *offset = off;
> -       return count;
> +       return rc;
>  }
>
>  static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
> --
> 2.24.0
>

[PATCH] [PATCH v2] fsi: fix bogus error returns from cfam_read and cfam_write

[Jeremy Kerr]

Based on a static analysis report and original patch from Colin Ian King
<colin.king@canonical.com>.

Currently, we may drop error values from cfam_read and cfam_write. This
change returns the actual error on failure, but a partial read/write will
take precedence.

Addresses-Coverity: ("Unused value")
Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

---
Colin: thanks for the report and patch. I think this is a more complete
fix, as we want to preseve any partial read/write status if a failure
happens mid-way through an operation. Let me know if you (or the
coverity analysis) have any feedback.

---

 drivers/fsi/fsi-core.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 71c6f9fef648..3158a78c2e94 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -699,6 +699,8 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
 	if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
 		return -EINVAL;
 
+	rc = 0;
+
 	for (total_len = 0; total_len < count; total_len += read_len) {
 		__be32 data;
 
@@ -707,18 +709,22 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
 
 		rc = fsi_slave_read(slave, off, &data, read_len);
 		if (rc)
-			goto fail;
+			break;
 		rc = copy_to_user(buf + total_len, &data, read_len);
 		if (rc) {
 			rc = -EFAULT;
-			goto fail;
+			break;
 		}
 		off += read_len;
 	}
-	rc = count;
- fail:
+
+	/* if we've read any data, we want that to be returned in
+	 * preference to an error state */
+	if (total_len)
+		rc = total_len;
+
 	*offset = off;
-	return count;
+	return rc;
 }
 
 static ssize_t cfam_write(struct file *filep, const char __user *buf,
@@ -736,6 +742,8 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
 	if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
 		return -EINVAL;
 
+	rc = 0;
+
 	for (total_len = 0; total_len < count; total_len += write_len) {
 		__be32 data;
 
@@ -745,17 +753,21 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
 		rc = copy_from_user(&data, buf + total_len, write_len);
 		if (rc) {
 			rc = -EFAULT;
-			goto fail;
+			break;
 		}
 		rc = fsi_slave_write(slave, off, &data, write_len);
 		if (rc)
-			goto fail;
+			break;
 		off += write_len;
 	}
-	rc = count;
- fail:
+
+	/* if we've written any data, we want to indicate that partial write
+	 * instead of any mid-stream error */
+	if (total_len)
+		rc = total_len;
+
 	*offset = off;
-	return count;
+	return rc;
 }
 
 static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
-- 
2.20.1

Re: [PATCH] [PATCH v2] fsi: fix bogus error returns from cfam_read and cfam_write

[Colin Ian King]

On 29/11/2019 03:24, Jeremy Kerr wrote:
> Based on a static analysis report and original patch from Colin Ian King
> <colin.king@canonical.com>.
> 
> Currently, we may drop error values from cfam_read and cfam_write. This
> change returns the actual error on failure, but a partial read/write will
> take precedence.
> 
> Addresses-Coverity: ("Unused value")
> Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
> Reported-by: Colin Ian King <colin.king@canonical.com>
> Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
> 
> ---
> Colin: thanks for the report and patch. I think this is a more complete
> fix, as we want to preseve any partial read/write status if a failure
> happens mid-way through an operation. Let me know if you (or the
> coverity analysis) have any feedback.

Looks good to me. Thanks Jeremy.



> 
> ---
> 
>  drivers/fsi/fsi-core.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
> index 71c6f9fef648..3158a78c2e94 100644
> --- a/drivers/fsi/fsi-core.c
> +++ b/drivers/fsi/fsi-core.c
> @@ -699,6 +699,8 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
>  	if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
>  		return -EINVAL;
>  
> +	rc = 0;
> +
>  	for (total_len = 0; total_len < count; total_len += read_len) {
>  		__be32 data;
>  
> @@ -707,18 +709,22 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
>  
>  		rc = fsi_slave_read(slave, off, &data, read_len);
>  		if (rc)
> -			goto fail;
> +			break;
>  		rc = copy_to_user(buf + total_len, &data, read_len);
>  		if (rc) {
>  			rc = -EFAULT;
> -			goto fail;
> +			break;
>  		}
>  		off += read_len;
>  	}
> -	rc = count;
> - fail:
> +
> +	/* if we've read any data, we want that to be returned in
> +	 * preference to an error state */
> +	if (total_len)
> +		rc = total_len;
> +
>  	*offset = off;
> -	return count;
> +	return rc;
>  }
>  
>  static ssize_t cfam_write(struct file *filep, const char __user *buf,
> @@ -736,6 +742,8 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
>  	if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
>  		return -EINVAL;
>  
> +	rc = 0;
> +
>  	for (total_len = 0; total_len < count; total_len += write_len) {
>  		__be32 data;
>  
> @@ -745,17 +753,21 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
>  		rc = copy_from_user(&data, buf + total_len, write_len);
>  		if (rc) {
>  			rc = -EFAULT;
> -			goto fail;
> +			break;
>  		}
>  		rc = fsi_slave_write(slave, off, &data, write_len);
>  		if (rc)
> -			goto fail;
> +			break;
>  		off += write_len;
>  	}
> -	rc = count;
> - fail:
> +
> +	/* if we've written any data, we want to indicate that partial write
> +	 * instead of any mid-stream error */
> +	if (total_len)
> +		rc = total_len;
> +
>  	*offset = off;
> -	return count;
> +	return rc;
>  }
>  
>  static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
>