linux-kernel - [PATCH 4.19 44/49] xen: unexport __init-annotated xen_xlate_map_ballooned

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Message-Id: <20220630133235.173427029@linuxfoundation.org>
Date:   Thu, 30 Jun 2022 15:46:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH 4.19 44/49] xen: unexport __init-annotated xen_xlate_map_ballooned_pages()

From: Masahiro Yamada <masahiroy@...nel.org>

commit dbac14a5a05ff8e1ce7c0da0e1f520ce39ec62ea upstream.

EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.

modpost used to detect it, but it has been broken for a decade.

Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.

There are two ways to fix it:

  - Remove __init
  - Remove EXPORT_SYMBOL

I chose the latter for this case because none of the in-tree call-sites
(arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as
modular.

Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common place")
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Acked-by: Stefano Stabellini <sstabellini@...nel.org>
Link: https://lore.kernel.org/r/20220606045920.4161881-1-masahiroy@kernel.org
Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/xen/xlate_mmu.c |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/xen/xlate_mmu.c
+++ b/drivers/xen/xlate_mmu.c
@@ -262,4 +262,3 @@ int __init xen_xlate_map_ballooned_pages
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(xen_xlate_map_ballooned_pages);