[PATCH 08/10] scsi: aic7xxx: aicasm: Replace snprintf() with the safer scnprintf() variant

Lee Jones posted 10 patches 1 year, 10 months ago
[PATCH 08/10] scsi: aic7xxx: aicasm: Replace snprintf() with the safer scnprintf() variant
Posted by Lee Jones 1 year, 10 months ago
There is a general misunderstanding amongst engineers that {v}snprintf()
returns the length of the data *actually* encoded into the destination
array.  However, as per the C99 standard {v}snprintf() really returns
the length of the data that *would have been* written if there were
enough space for it.  This misunderstanding has led to buffer-overruns
in the past.  It's generally considered safer to use the {v}scnprintf()
variants in their place (or even sprintf() in simple cases).  So let's
do that.

Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Signed-off-by: Lee Jones <lee@kernel.org>
---
Cc: Hannes Reinecke <hare@suse.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Lee Jones <lee@kernel.org>
Cc: linux-scsi@vger.kernel.org
---
 drivers/scsi/aic7xxx/aicasm/aicasm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/aic7xxx/aicasm/aicasm.c b/drivers/scsi/aic7xxx/aicasm/aicasm.c
index 8d995186e557a..bc758e78d3c06 100644
--- a/drivers/scsi/aic7xxx/aicasm/aicasm.c
+++ b/drivers/scsi/aic7xxx/aicasm/aicasm.c
@@ -331,7 +331,7 @@ back_patch()
 			if (cur_instr->patch_label->type != LABEL) {
 				char buf[255];
 
-				snprintf(buf, sizeof(buf),
+				scnprintf(buf, sizeof(buf),
 					 "Undefined label %s",
 					 cur_instr->patch_label->name);
 				stop(buf, EX_DATAERR);
-- 
2.43.0.594.gd9cf4e227d-goog
Re: [PATCH 08/10] scsi: aic7xxx: aicasm: Replace snprintf() with the safer scnprintf() variant
Posted by Kees Cook 1 year, 10 months ago
On Thu, Feb 08, 2024 at 08:44:20AM +0000, Lee Jones wrote:
> There is a general misunderstanding amongst engineers that {v}snprintf()
> returns the length of the data *actually* encoded into the destination
> array.  However, as per the C99 standard {v}snprintf() really returns
> the length of the data that *would have been* written if there were
> enough space for it.  This misunderstanding has led to buffer-overruns
> in the past.  It's generally considered safer to use the {v}scnprintf()
> variants in their place (or even sprintf() in simple cases).  So let's
> do that.
> 
> Link: https://lwn.net/Articles/69419/
> Link: https://github.com/KSPP/linux/issues/105
> Signed-off-by: Lee Jones <lee@kernel.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook