scs: Report SCS usage in bytes rather than number of entries

willdeacon · willdeacon · commit 333ed74689b8 · 2020-06-04T16:14:56.000+01:00
Fix the SCS debug usage check so that we report the number of bytes used, rather than the number of entries. Fixes: 5bbaf9d ("scs: Add support for stack usage debugging") Reported-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/kernel/scs.c b/kernel/scs.c
@@ -74,7 +74,7 @@ static void scs_check_usage(struct task_struct *tsk)
 	for (p = task_scs(tsk); p < __scs_magic(tsk); ++p) {
 		if (!READ_ONCE_NOCHECK(*p))
 			break;
-		used++;
+		used += sizeof(*p);
 	}
 
 	while (used > curr) {

Original file line number	Diff line number	Diff line change
`@@ -74,7 +74,7 @@ static void scs_check_usage(struct task_struct *tsk)`
`74`	`74`	`for (p = task_scs(tsk); p < __scs_magic(tsk); ++p) {`
`75`	`75`	`if (!READ_ONCE_NOCHECK(*p))`
`76`	`76`	`break;`
`77`		`- used++;`
	`77`	`+ used += sizeof(*p);`
`78`	`78`	`}`
`79`	`79`
`80`	`80`	`while (used > curr) {`