linux-kernel - [PATCH] ubifs: Fix uninitialized variable in search_dh

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Date:   Sun, 17 Sep 2017 10:32:20 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Richard Weinberger <richard@....at>,
        Artem Bityutskiy <dedekind1@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     Hyunchul Lee <hyc.lee@...il.com>,
        Colin Ian King <colin.king@...onical.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] ubifs: Fix uninitialized variable in search_dh_cookie()

fs/ubifs/tnc.c: In function ‘search_dh_cookie’:
fs/ubifs/tnc.c:1893: warning: ‘err’ is used uninitialized in this function

Indeed, err is always used uninitialized.

According to an original review comment from Hyunchul, acknowledged by
Richard, err should be initialized to -ENOENT to avoid the first call to
tnc_next().  But we can achieve the same by reordering the code.

Reported-by: Hyunchul Lee <hyc.lee@...il.com>
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
Compile-tested only.

Still needed in v4.14-rc1, so I'm sending out the patch I wrote in July.
This avoids initializing err at the top, so we don't loose the ability to
catch future uninitialized use.
---
 fs/ubifs/tnc.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 0a213dcba2a1f0f5..ba3d0e0f86151e53 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -1890,35 +1890,28 @@ static int search_dh_cookie(struct ubifs_info *c, const union ubifs_key *key,
 	union ubifs_key *dkey;
 
 	for (;;) {
-		if (!err) {
-			err = tnc_next(c, &znode, n);
-			if (err)
-				goto out;
-		}
-
 		zbr = &znode->zbranch[*n];
 		dkey = &zbr->key;
 
 		if (key_inum(c, dkey) != key_inum(c, key) ||
 		    key_type(c, dkey) != key_type(c, key)) {
-			err = -ENOENT;
-			goto out;
+			return -ENOENT;
 		}
 
 		err = tnc_read_hashed_node(c, zbr, dent);
 		if (err)
-			goto out;
+			return err;
 
 		if (key_hash(c, key) == key_hash(c, dkey) &&
 		    le32_to_cpu(dent->cookie) == cookie) {
 			*zn = znode;
-			goto out;
+			return 0;
 		}
-	}
-
-out:
 
-	return err;
+		err = tnc_next(c, &znode, n);
+		if (err)
+			return err;
+	}
 }
 
 static int do_lookup_dh(struct ubifs_info *c, const union ubifs_key *key,
-- 
2.7.4