gcc-10: avoid shadowing standard library 'free()' in crypto

BugLink: https://bugs.launchpad.net/bugs/1879759
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: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/crypto/lrw.c b/crypto/lrw.c
index be829f6afc8e5bbcf6fabec3a0135740b1cb966c..3d40e1f32beaeaf040e8c6d01016d94dc95ce9f2 100644 (file)
--- a/crypto/lrw.c
+++ b/crypto/lrw.c
@@ -289,7 +289,7 @@ static void exit_tfm(struct crypto_skcipher *tfm)
        crypto_free_skcipher(ctx->child);
 }
 
-static void free(struct skcipher_instance *inst)
+static void free_inst(struct skcipher_instance *inst)
 {
        crypto_drop_skcipher(skcipher_instance_ctx(inst));
        kfree(inst);
@@ -401,7 +401,7 @@ static int create(struct crypto_template *tmpl, struct rtattr **tb)
        inst->alg.encrypt = encrypt;
        inst->alg.decrypt = decrypt;
 
-       inst->free = free;
+       inst->free = free_inst;
 
        err = skcipher_register_instance(tmpl, inst);
        if (err)

diff --git a/crypto/xts.c b/crypto/xts.c
index ab117633d64e775520a6ab542282e4a839a8a714..9d72429f666ee74b2e7d520ab51d29006749d00f 100644 (file)
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -328,7 +328,7 @@ static void exit_tfm(struct crypto_skcipher *tfm)
        crypto_free_cipher(ctx->tweak);
 }
 
-static void free(struct skcipher_instance *inst)
+static void free_inst(struct skcipher_instance *inst)
 {
        crypto_drop_skcipher(skcipher_instance_ctx(inst));
        kfree(inst);
@@ -439,7 +439,7 @@ static int create(struct crypto_template *tmpl, struct rtattr **tb)
        inst->alg.encrypt = encrypt;
        inst->alg.decrypt = decrypt;
 
-       inst->free = free;
+       inst->free = free_inst;
 
        err = skcipher_register_instance(tmpl, inst);
        if (err)