From b9da30e8f2590dfe3fae15eef10b728e103b3b6c Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 9 May 2020 15:58:04 -0700
Subject: [PATCH] gcc-10: avoid shadowing standard library 'free()' in crypto
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BugLink: https://bugs.launchpad.net/bugs/1881356

commit 1a263ae60b04de959d9ce9caea4889385eefcc7b upstream.

gcc-10 has started warning about conflicting types for a few new
built-in functions, particularly 'free()'.

This results in warnings like:

   crypto/xts.c:325:13: warning: conflicting types for built-in function ‘free’; expected ‘void(void *)’ [-Wbuiltin-declaration-mismatch]

because the crypto layer had its local freeing functions called
'free()'.

Gcc-10 is in the wrong here, since that function is marked 'static', and
thus there is no chance of confusion with any standard library function
namespace.

But the simplest thing to do is to just use a different name here, and
avoid this gcc mis-feature.

[ Side note: gcc knowing about 'free()' is in itself not the
  mis-feature: the semantics of 'free()' are special enough that a
  compiler can validly do special things when seeing it.

  So the mis-feature here is that gcc thinks that 'free()' is some
  restricted name, and you can't shadow it as a local static function.

  Making the special 'free()' semantics be a function attribute rather
  than tied to the name would be the much better model ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>
---
 crypto/lrw.c | 4 ++--
 crypto/xts.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/crypto/lrw.c b/crypto/lrw.c
index d38a382b09eb..fc3d4fec8ddd 100644
--- a/crypto/lrw.c
+++ b/crypto/lrw.c
@@ -377,7 +377,7 @@ static struct crypto_instance *alloc(struct rtattr **tb)
 	return inst;
 }
 
-static void free(struct crypto_instance *inst)
+static void free_inst(struct crypto_instance *inst)
 {
 	crypto_drop_spawn(crypto_instance_ctx(inst));
 	kfree(inst);
@@ -386,7 +386,7 @@ static void free(struct crypto_instance *inst)
 static struct crypto_template crypto_tmpl = {
 	.name = "lrw",
 	.alloc = alloc,
-	.free = free,
+	.free = free_inst,
 	.module = THIS_MODULE,
 };
 
diff --git a/crypto/xts.c b/crypto/xts.c
index 26ba5833b994..d37cf4f2f8ff 100644
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -329,7 +329,7 @@ static struct crypto_instance *alloc(struct rtattr **tb)
 	return inst;
 }
 
-static void free(struct crypto_instance *inst)
+static void free_inst(struct crypto_instance *inst)
 {
 	crypto_drop_spawn(crypto_instance_ctx(inst));
 	kfree(inst);
@@ -338,7 +338,7 @@ static void free(struct crypto_instance *inst)
 static struct crypto_template crypto_tmpl = {
 	.name = "xts",
 	.alloc = alloc,
-	.free = free,
+	.free = free_inst,
 	.module = THIS_MODULE,
 };
 
-- 
2.30.9