linux-hardening - [PATCH 09/17] lib/list_sort: fix function type mismatches

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Date:   Thu, 11 Mar 2021 16:49:11 -0800
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>, Jessica Yu <jeyu@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
        bpf@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kbuild@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 09/17] lib/list_sort: fix function type mismatches

Casting the comparison function to a different type trips indirect
call Control-Flow Integrity (CFI) checking. Remove the additional
consts from cmp_func, and the now unneeded casts.

Fixes: 043b3f7b6388 ("lib/list_sort: simplify and remove MAX_LIST_LENGTH_BITS")
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 lib/list_sort.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/list_sort.c b/lib/list_sort.c
index 52f0c258c895..b14accf4ef83 100644
--- a/lib/list_sort.c
+++ b/lib/list_sort.c
@@ -8,7 +8,7 @@
 #include <linux/list.h>
 
 typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *,
-		struct list_head const *, struct list_head const *);
+		struct list_head *, struct list_head *);
 
 /*
  * Returns a list organized in an intermediate format suited
@@ -227,7 +227,7 @@ void list_sort(void *priv, struct list_head *head,
 		if (likely(bits)) {
 			struct list_head *a = *tail, *b = a->prev;
 
-			a = merge(priv, (cmp_func)cmp, b, a);
+			a = merge(priv, cmp, b, a);
 			/* Install the merged result in place of the inputs */
 			a->prev = b->prev;
 			*tail = a;
@@ -249,10 +249,10 @@ void list_sort(void *priv, struct list_head *head,
 
 		if (!next)
 			break;
-		list = merge(priv, (cmp_func)cmp, pending, list);
+		list = merge(priv, cmp, pending, list);
 		pending = next;
 	}
 	/* The final merge, rebuilding prev links */
-	merge_final(priv, (cmp_func)cmp, head, pending, list);
+	merge_final(priv, cmp, head, pending, list);
 }
 EXPORT_SYMBOL(list_sort);
-- 
2.31.0.rc2.261.g7f71774620-goog