[PATCH] net/ethernet/intel/ixgbe/ixgbe_debugfs.c: fix error handling in ixgbe_dbg_reg_ops_read().

[PATCH] net/ethernet/intel/ixgbe/ixgbe_debugfs.c: fix error handling in ixgbe_dbg_reg_ops_read().

[Cyril Roelandt]

copy_to_user() cannot return a negative value: it returns the number of bytes
that could not be copied.

Return -EFAULT on failure rather than the number of bytes that could not be
copied, as this seems more standard.

Signed-off-by: Cyril Roelandt <tipecaml@gmail.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_debugfs.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_debugfs.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_debugfs.c
index 8d3a218..77a3598 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_debugfs.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_debugfs.c
@@ -62,7 +62,6 @@ static ssize_t ixgbe_dbg_reg_ops_read(struct file *filp, char __user *buffer,
 {
 	struct ixgbe_adapter *adapter = filp->private_data;
 	char buf[256];
-	int bytes_not_copied;
 	int len;
 
 	/* don't allow partial reads */
@@ -73,9 +72,8 @@ static ssize_t ixgbe_dbg_reg_ops_read(struct file *filp, char __user *buffer,
 		       adapter->netdev->name, ixgbe_dbg_reg_ops_buf);
 	if (count < len)
 		return -ENOSPC;
-	bytes_not_copied = copy_to_user(buffer, buf, len);
-	if (bytes_not_copied < 0)
-		return bytes_not_copied;
+	if (copy_to_user(buffer, buf, len) > 0)
+		return -EFAULT;
 
 	*ppos = len;
 	return len;
-- 
1.7.10.4

Re: [PATCH] net/ethernet/intel/ixgbe/ixgbe_debugfs.c: fix error handling in ixgbe_dbg_reg_ops_read().

[Jeff Kirsher]

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On Fri, 2012-11-16 at 04:26 +0100, Cyril Roelandt wrote:
> 
> copy_to_user() cannot return a negative value: it returns the number
> of bytes
> that could not be copied.
> 
> Return -EFAULT on failure rather than the number of bytes that could
> not be
> copied, as this seems more standard.
> 
> Signed-off-by: Cyril Roelandt <tipecaml@gmail.com>
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_debugfs.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-) 

Actually, I already have a similar patch in my queue reported by Dan
Carpenter, and created by Josh Hay which fixes this issue.  I should be
pushing the patch in my queue in the next week.  Here is the patch I am
referring to:

ixgbe: eliminate Smatch warnings in ixgbe_debugfs.c
    
This patch replaces calls to copy_to_user, copy_from_user, and the
associated logic, with calls to simple_read_from_buffer and
simple_write_to_buffer respectively.  This was done to eliminate
warnings generated by the Smatch static analysis tool.
    
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Josh Hay <joshua.a.hay@intel.com>

Cheers,
Jeff

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