linux-kernel - Re: [PATCH][RESEND] Fix a potential NULL pointer deref in the aic7xxx, ahc_print

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Date:	Sun, 5 Aug 2007 17:52:05 +0200
From:	Jesper Juhl <jesper.juhl@...il.com>
To:	"Justin T. Gibbs" <gibbs@...iguy.com>
Cc:	James Bottomley <James.Bottomley@...eleye.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Bottomley <jejb@...nel.org>, linux-scsi@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesper Juhl <jesper.juhl@...il.com>
Subject: Re: [PATCH][RESEND] Fix a potential NULL pointer deref in the aic7xxx, ahc_print_register() function

On Sunday 05 August 2007 17:42:31 Justin T. Gibbs wrote:
> All of this logic was simplified back in '05 in the BSD drivers by adding
> this to the top of the function:
> 
>         u_int   dummy_column;
>   
>         if (cur_column == NULL) {
>                 dummy_column = 0;
>                 cur_column = &dummy_column;
>         }
> 
> and then stripping out the cur_column == NULL checks in the routine.
> 

Thank you for that info.

James, if that sounds like a better way to deal with it to you, then 
here's a patch to implement it.



Signed-off-by: Jesper Juhl <jesper.juhl@...il.com>
---

 drivers/scsi/aic7xxx/aic7xxx_core.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/aic7xxx/aic7xxx_core.c b/drivers/scsi/aic7xxx/aic7xxx_core.c
index 75733b0..d1f3f25 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_core.c
+++ b/drivers/scsi/aic7xxx/aic7xxx_core.c
@@ -6529,8 +6529,14 @@ ahc_print_register(ahc_reg_parse_entry_t *table, u_int num_entries,
 {
 	int	printed;
 	u_int	printed_mask;
+	u_int	dummy_column;
 
-	if (cur_column != NULL && *cur_column >= wrap_point) {
+	if (!cur_column) {
+		dummy_column = 0;
+		cur_column = &dummy_column;
+	}
+
+	if (*cur_column >= wrap_point) {
 		printf("\n");
 		*cur_column = 0;
 	}
@@ -6565,8 +6571,7 @@ ahc_print_register(ahc_reg_parse_entry_t *table, u_int num_entries,
 		printed += printf(") ");
 	else
 		printed += printf(" ");
-	if (cur_column != NULL)
-		*cur_column += printed;
+	*cur_column += printed;
 	return (printed);
 }
 


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