[PATCH net v2] fddi: skfp: fix null pointer deferenece in smt.c

[PATCH net v2] fddi: skfp: fix null pointer deferenece in smt.c

[Siddarth Gundu]

In smt_string_swap(), when a closing bracket ']' is encountered
before any opening bracket '[' open_paren would be NULL,
and assigning it to format would lead to a null pointer being
dereferenced in the format++ statement.

Add a check to verify open_paren is non-NULL before assigning
it to format

This issue was reported by Coverity Scan.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Siddarth Gundu <siddarthsgml@gmail.com>
---
v2:
 - fix commit message
 - Add mention of Coverity Scan
 - Update Fixes tag to reference initial commit
v1: https://lore.kernel.org/all/20250505091025.27368-1-siddarthsgml@gmail.com/

 drivers/net/fddi/skfp/smt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/fddi/skfp/smt.c b/drivers/net/fddi/skfp/smt.c
index dd15af4e98c2..174f279b89ac 100644
--- a/drivers/net/fddi/skfp/smt.c
+++ b/drivers/net/fddi/skfp/smt.c
@@ -1857,7 +1857,8 @@ static void smt_string_swap(char *data, const char *format, int len)
 			open_paren = format ;
 			break ;
 		case ']' :
-			format = open_paren ;
+			if (open_paren)
+				format = open_paren ;
 			break ;
 		case '1' :
 		case '2' :
-- 
2.43.0

Re: [PATCH net v2] fddi: skfp: fix null pointer deferenece in smt.c

[Jakub Kicinski]

On Thu,  8 May 2025 02:07:06 +0530 Siddarth Gundu wrote:
> In smt_string_swap(), when a closing bracket ']' is encountered
> before any opening bracket '[' open_paren would be NULL,
> and assigning it to format would lead to a null pointer being
> dereferenced in the format++ statement.
> 
> Add a check to verify open_paren is non-NULL before assigning
> it to format

You'd have to explain where an invalid format could come from.
As far as I can tell they are all hardcoded (grep for SWAP_SMT)
-- 
pw-bot: cr