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Commit 2ebc3464 authored by Dan Rosenberg's avatar Dan Rosenberg Committed by Chris Mason
Browse files

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: default avatarDan Rosenberg <dan.j.rosenberg@gmail.com>
cc: stable@kernel.org
Signed-off-by: default avatarChris 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;