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>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 2a8b3a7..9254b3d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1458,7 +1458,7 @@
*/
/* 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 @@
/* 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;