From: Scott Bauer <sbauer@plzdonthack.me>
Date: Thu, 28 Jul 2016 01:11:29 +0000 (-0600)
Subject: vfs: ioctl: prevent double-fetch in dedupe ioctl
X-Git-Tag: v4.8-rc1~120
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=10eec60ce79187686e052092e5383c99b4420a20;p=platform%2Fkernel%2Flinux-exynos.git

vfs: ioctl: prevent double-fetch in dedupe ioctl

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@plzdonthack.me>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 116a333..0f56deb 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -590,6 +590,7 @@ static long ioctl_file_dedupe_range(struct file *file, void __user *arg)
 		goto out;
 	}
 
+	same->dest_count = count;
 	ret = vfs_dedupe_file_range(file, same);
 	if (ret)
 		goto out;