linux-kernel - [PATCH 4.7 02/41] vfs: ioctl: prevent double-fetch in dedupe ioctl

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Date:	Sun, 14 Aug 2016 22:38:28 +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, Scott Bauer <sbauer@...donthack.me>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.7 02/41] vfs: ioctl: prevent double-fetch in dedupe ioctl

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Scott Bauer <sbauer@...donthack.me>

commit 10eec60ce79187686e052092e5383c99b4420a20 upstream.

This prevents a double-fetch from user space that can lead to to an
undersized allocation and heap overflow.

Fixes: 54dbc1517237 ("vfs: hoist the btrfs deduplication ioctl to the vfs")
Signed-off-by: Scott Bauer <sbauer@...donthack.me>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ioctl.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -590,6 +590,7 @@ static long ioctl_file_dedupe_range(stru
 		goto out;
 	}
 
+	same->dest_count = count;
 	ret = vfs_dedupe_file_range(file, same);
 	if (ret)
 		goto out;