[PATCH v6 01/10] of: fix out-of-bounds read in of_alias_scan() stem parser

The stem parser tests isdigit(*(end - 1)) before checking end > start
and so reads one byte before the property name when the name is empty
or all digits. Check the bound first.

Fixes: 611cad720148 ("dt: add of_alias_scan and of_alias_get_id")
Cc: [email protected]
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <[email protected]>
---
 drivers/of/base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 6e7a42dedad3..477017ed6f49 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1967,7 +1967,7 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
 
 		/* walk the alias backwards to extract the id and work out
 		 * the 'stem' string */
-		while (isdigit(*(end-1)) && end > start)
+		while (end > start && isdigit(*(end - 1)))
 			end--;
 		len = end - start;
 

-- 
2.54.0