[PATCH v2] drivers/edac/edac_mc: Remove all strcpy() uses

[PATCH v2] drivers/edac/edac_mc: Remove all strcpy() uses

[Len Baker]

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. The safe replacement is strscpy().

This is a previous step in the path to remove the strcpy() function
entirely from the kernel.

Signed-off-by: Len Baker <len.baker@gmx.com>
---
This is a task of the KSPP [1]

[1] https://github.com/KSPP/linux/issues/88

Changelog v1 -> v2
- Use the strscpy() instead of scnprintf() to add labels and follow a
  code pattern more similar to the current one (advance "p" and
  decrement "left") (Robert Richter).

 drivers/edac/edac_mc.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index f6d462d0be2d..13b50be22ba6 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -1032,6 +1032,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 	int i, n_labels = 0;
 	struct edac_raw_error_desc *e = &mci->error_desc;
 	bool any_memory = true;
+	size_t left;

 	edac_dbg(3, "MC%d\n", mci->mc_idx);

@@ -1086,6 +1087,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 	 */
 	p = e->label;
 	*p = '\0';
+	left = sizeof(e->label);

 	mci_for_each_dimm(mci, dimm) {
 		if (top_layer >= 0 && top_layer != dimm->location[0])
@@ -1114,10 +1116,12 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 			*p = '\0';
 		} else {
 			if (p != e->label) {
-				strcpy(p, OTHER_LABEL);
+				strscpy(p, OTHER_LABEL, left);
+				left -= strlen(OTHER_LABEL);
 				p += strlen(OTHER_LABEL);
 			}
-			strcpy(p, dimm->label);
+			strscpy(p, dimm->label, left);
+			left -= strlen(p);
 			p += strlen(p);
 		}

@@ -1140,9 +1144,9 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 	}

 	if (any_memory)
-		strcpy(e->label, "any memory");
+		strscpy(e->label, "any memory", sizeof(e->label));
 	else if (!*e->label)
-		strcpy(e->label, "unknown memory");
+		strscpy(e->label, "unknown memory", sizeof(e->label));

 	edac_inc_csrow(e, row, chan);

--
2.25.1

Re: [PATCH v2] drivers/edac/edac_mc: Remove all strcpy() uses

[Robert Richter]

On 01.08.21 16:35:58, Len Baker wrote:

> @@ -1114,10 +1116,12 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  			*p = '\0';
>  		} else {
>  			if (p != e->label) {
> -				strcpy(p, OTHER_LABEL);
> +				strscpy(p, OTHER_LABEL, left);
> +				left -= strlen(OTHER_LABEL);
>  				p += strlen(OTHER_LABEL);

Those both must be strlen(p) now as otherwise 'left' could underflow
(and p overflow).

-Robert

>  			}
> -			strcpy(p, dimm->label);
> +			strscpy(p, dimm->label, left);
> +			left -= strlen(p);
>  			p += strlen(p);
>  		}
> 

Re: [PATCH v2] drivers/edac/edac_mc: Remove all strcpy() uses

[Robert Richter]

On 02.08.21 11:19:33, Robert Richter wrote:
> On 01.08.21 16:35:58, Len Baker wrote:
> 
> > @@ -1114,10 +1116,12 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
> >  			*p = '\0';
> >  		} else {
> >  			if (p != e->label) {
> > -				strcpy(p, OTHER_LABEL);
> > +				strscpy(p, OTHER_LABEL, left);
> > +				left -= strlen(OTHER_LABEL);

Another note: Other parts of the code use 'len' instead of 'left', so
if you could change that too?

Thanks,

-Robert

> >  				p += strlen(OTHER_LABEL);
> 
> Those both must be strlen(p) now as otherwise 'left' could underflow
> (and p overflow).
> 
> -Robert
> 
> >  			}
> > -			strcpy(p, dimm->label);
> > +			strscpy(p, dimm->label, left);
> > +			left -= strlen(p);
> >  			p += strlen(p);
> >  		}
> >