linux-kernel - [PATCH 5.4 39/68] cifs: fix a sign extension bug

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Message-Id: <20210927170221.323585557@linuxfoundation.org>
Date:   Mon, 27 Sep 2021 19:02:35 +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, Dan Carpenter <dan.carpenter@...cle.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 39/68] cifs: fix a sign extension bug

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit e946d3c887a9dc33aa82a349c6284f4a084163f4 ]

The problem is the mismatched types between "ctx->total_len" which is
an unsigned int, "rc" which is an int, and "ctx->rc" which is a
ssize_t.  The code does:

	ctx->rc = (rc == 0) ? ctx->total_len : rc;

We want "ctx->rc" to store the negative "rc" error code.  But what
happens is that "rc" is type promoted to a high unsigned int and
'ctx->rc" will store the high positive value instead of a negative
value.

The fix is to change "rc" from an int to a ssize_t.

Fixes: c610c4b619e5 ("CIFS: Add asynchronous write support through kernel AIO")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 1aac8d38f887..a9746af5a44d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2989,7 +2989,7 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
 	struct cifs_tcon *tcon;
 	struct cifs_sb_info *cifs_sb;
 	struct dentry *dentry = ctx->cfile->dentry;
-	int rc;
+	ssize_t rc;
 
 	tcon = tlink_tcon(ctx->cfile->tlink);
 	cifs_sb = CIFS_SB(dentry->d_sb);
-- 
2.33.0