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From:   Miklos Szeredi <mszeredi@redhat.com>
To:     "Eric W . Biederman" <ebiederm@xmission.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 02/10] vfs: verify source area in vfs_dedupe_file_range_one()
Date:   Mon,  7 Dec 2020 17:32:47 +0100
Message-Id: <20201207163255.564116-3-mszeredi@redhat.com>
In-Reply-To: <20201207163255.564116-1-mszeredi@redhat.com>
References: <20201207163255.564116-1-mszeredi@redhat.com>
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Call remap_verify_area() on the source file as well as the destination.

When called from vfs_dedupe_file_range() the check as already been
performed, but not so if called from layered fs (overlayfs, etc...)

Could ommit the redundant check in vfs_dedupe_file_range(), but leave for
now to get error early (for fear of breaking backward compatibility).

This call shouldn't be performance sensitive.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/remap_range.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/remap_range.c b/fs/remap_range.c
index e6099beefa97..77dba3a49e65 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -456,8 +456,16 @@ loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
 	if (ret)
 		return ret;
 
+	/*
+	 * This is redundant if called from vfs_dedupe_file_range(), but other
+	 * callers need it and it's not performance sesitive...
+	 */
+	ret = remap_verify_area(src_file, src_pos, len, false);
+	if (ret)
+		goto out_drop_write;
+
 	ret = remap_verify_area(dst_file, dst_pos, len, true);
-	if (ret < 0)
+	if (ret)
 		goto out_drop_write;
 
 	ret = -EPERM;
-- 
2.26.2