[patch] efi: locking fix in efivar_entry_set_safe()

[patch] efi: locking fix in efivar_entry_set_safe()

[Dan Carpenter]

The intent is that if we aren't allowed to block because we're in an
NMI or an emergency then we only take the lock if it is uncontended.

Part of the problem is the test is reversed so we return -EBUSY if we
acquire the lock.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
Static checker stuff.  I haven't tested this.

diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 1d80c1c..f34d8fe 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -622,10 +622,12 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
 	if (!ops->query_variable_store)
 		return -ENOSYS;
 
-	if (!block && spin_trylock_irqsave(&__efivars->lock, flags))
-		return -EBUSY;
-	else
+	if (!block) {
+		if (!spin_trylock_irqsave(&__efivars->lock, flags))
+			return -EBUSY;
+	} else {
 		spin_lock_irqsave(&__efivars->lock, flags);
+	}
 
 	status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
 	if (status != EFI_SUCCESS) {

Re: [patch] efi: locking fix in efivar_entry_set_safe()

[Matt Fleming]

On 30/04/13 08:43, Dan Carpenter wrote:
> The intent is that if we aren't allowed to block because we're in an
> NMI or an emergency then we only take the lock if it is uncontended.
> 
> Part of the problem is the test is reversed so we return -EBUSY if we
> acquire the lock.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> Static checker stuff.  I haven't tested this.

This looks correct to me. Thanks!

> diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> index 1d80c1c..f34d8fe 100644
> --- a/drivers/firmware/efi/vars.c
> +++ b/drivers/firmware/efi/vars.c
> @@ -622,10 +622,12 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
>  	if (!ops->query_variable_store)
>  		return -ENOSYS;
>  
> -	if (!block && spin_trylock_irqsave(&__efivars->lock, flags))
> -		return -EBUSY;
> -	else
> +	if (!block) {
> +		if (!spin_trylock_irqsave(&__efivars->lock, flags))
> +			return -EBUSY;
> +	} else {
>  		spin_lock_irqsave(&__efivars->lock, flags);
> +	}
>  
>  	status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
>  	if (status != EFI_SUCCESS) {


-- 
Matt Fleming, Intel Open Source Technology Center