Re: [PATCH v4] smb: client: fix heap overflow in cifs_do_set_acl()

[Paulo Alcantara <pc@manguebit.org>]

Frank Sorenson <sorenson@redhat.com> writes:

> cifs_set_acl() validates ACL size using posix_acl_xattr_size():
>
>         4 + (count * 8)  // 4-byte header + 8 bytes per ACE
>
> cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS
> wire format into the same buffer:
>
>         6 + (count * 10)  // 6-byte header + 10 bytes per ACE
>
> An ACL that passes the xattr-based check in cifs_set_acl() can
> overflow the heap when posix_acl_to_cifs() writes the larger CIFS
> format.
>
> Validate the CIFS format size against the remaining buffer space and
> USHRT_MAX before converting--data_count is __u16, so sizes above
> USHRT_MAX truncate the on-wire packet length, causing the server to
> apply a partial ACL.  Replace MaxDataCount = 1000 with
> min(CIFSMaxBufSize, USHRT_MAX).
> ...

Applied.