linux-kernel - [PATCH] f2fs: Eliminate usage of uninitialized

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Message-ID: <20200615040212.3681503-1-yanaijie@huawei.com>
Date:   Mon, 15 Jun 2020 12:02:12 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     <jaegeuk@...nel.org>, <chao@...nel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
CC:     <kernel-hardening@...ts.openwall.com>,
        Jason Yan <yanaijie@...wei.com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH] f2fs: Eliminate usage of uninitialized_var() macro

This is an effort to eliminate the uninitialized_var() macro[1].

The use of this macro is the wrong solution because it forces off ANY
analysis by the compiler for a given variable. It even masks "unused
variable" warnings.

Quoted from Linus[2]:

"It's a horrible thing to use, in that it adds extra cruft to the
source code, and then shuts up a compiler warning (even the _reliable_
warnings from gcc)."

The gcc option "-Wmaybe-uninitialized" has been disabled and this change
will not produce any warnnings even with "make W=1".

[1] https://github.com/KSPP/linux/issues/81
[2] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Cc: Kees Cook <keescook@...omium.org>
Signed-off-by: Jason Yan <yanaijie@...wei.com>
---
 fs/f2fs/data.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 326c63879ddc..e6ec61274d76 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2856,7 +2856,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
 	};
 #endif
 	int nr_pages;
-	pgoff_t uninitialized_var(writeback_index);
+	pgoff_t writeback_index;
 	pgoff_t index;
 	pgoff_t end;		/* Inclusive */
 	pgoff_t done_index;
-- 
2.25.4