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When a UHID_CREATE command is written to the uhid char device, a copy_from_user() is done from a user pointer embedded in the command. When the address limit is KERNEL_DS, e.g. as is the case during sys_sendfile(), this can read from kernel memory. Alternatively, information can be leaked from a setuid binary that is tricked to write to the file descriptor. Therefore, forbid UHID_CREATE in these cases. No other commands in uhid_char_write() are affected by this bug and UHID_CREATE is marked as "obsolete", so apply the restriction to UHID_CREATE only rather than to uhid_char_write() entirely. Thanks to Dmitry Vyukov for adding uhid definitions to syzkaller and to Jann Horn for commit9da3f2b740("x86/fault: BUG() when uaccess helpers fault on kernel addresses"), allowing this bug to be found. Reported-by: syzbot+72473edc9bf4eb1c6556@syzkaller.appspotmail.com Fixes:d365c6cfd3("HID: uhid: add UHID_CREATE and UHID_DESTROY events") Cc: <stable@vger.kernel.org> # v3.6+ Cc: Jann Horn <jannh@google.com> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Jann Horn <jannh@google.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.