Commit 2ebc3464 authored Jul 19, 2010 by Dan Rosenberg Committed by Chris Mason Jul 19, 2010

Btrfs: fix checks in BTRFS_IOC_CLONE_RANGE



1.  The BTRFS_IOC_CLONE and BTRFS_IOC_CLONE_RANGE ioctls should check
whether the donor file is append-only before writing to it.

2.  The BTRFS_IOC_CLONE_RANGE ioctl appears to have an integer
overflow that allows a user to specify an out-of-bounds range to copy
from the source file (if off + len wraps around).  I haven't been able
to successfully exploit this, but I'd imagine that a clever attacker
could use this to read things he shouldn't.  Even if it's not
exploitable, it couldn't hurt to be safe.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
cc: stable@kernel.org
Signed-off-by: Chris Mason <chris.mason@oracle.com>

parent b5384d48

fs/btrfs/ioctl.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1458,7 +1458,7 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
		*/

		/* the destination must be opened for writing */
		if (!(file->f_mode & FMODE_WRITE))
		if (!(file->f_mode & FMODE_WRITE) \|\| (file->f_flags & O_APPEND))
		return -EINVAL;

		ret = mnt_want_write(file->f_path.mnt);
		@@ -1511,7 +1511,7 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,

		/* determine range to clone */
		ret = -EINVAL;
		if (off >= src->i_size \|\| off + len > src->i_size)
		if (off + len > src->i_size \|\| off + len < off)
		goto out_unlock;
		if (len == 0)
		olen = len = src->i_size - off;

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