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Subject[047/205] Btrfs: fix checks in BTRFS_IOC_CLONE_RANGE
2.6.34-stable review patch.  If anyone has any objections, please let us know.

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

From: Dan Rosenberg <dan.j.rosenberg@gmail.com>

commit 2ebc3464781ad24474abcbd2274e6254689853b5 upstream.

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>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/btrfs/ioctl.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1469,7 +1469,7 @@ static noinline long btrfs_ioctl_clone(s
*/

/* 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);
@@ -1522,7 +1522,7 @@ static noinline long btrfs_ioctl_clone(s

/* 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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