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Breno Leitao
d084633868
commit f11274396a upstream.
uref->usage_index can be indirectly controlled by userspace, hence leading
to a potential exploitation of the Spectre variant 1 vulnerability.
This field is used as an array index by the hiddev_ioctl_usage() function,
when 'cmd' is either HIDIOCGCOLLECTIONINDEX, HIDIOCGUSAGES or
HIDIOCSUSAGES.
For cmd == HIDIOCGCOLLECTIONINDEX case, uref->usage_index is compared to
field->maxusage and then used as an index to dereference field->usage
array. The same thing happens to the cmd == HIDIOC{G,S}USAGES cases, where
uref->usage_index is checked against an array maximum value and then it is
used as an index in an array.
This is a summary of the HIDIOCGCOLLECTIONINDEX case, which matches the
traditional Spectre V1 first load:
copy_from_user(uref, user_arg, sizeof(*uref))
if (uref->usage_index >= field->maxusage)
goto inval;
i = field->usage[uref->usage_index].collection_index;
return i;
This patch fixes this by sanitizing field uref->usage_index before using it
to index field->usage (HIDIOCGCOLLECTIONINDEX) or field->value in
HIDIOC{G,S}USAGES arrays, thus, avoiding speculation in the first load.
Cc: <stable@vger.kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
v2: Contemplate cmd == HIDIOC{G,S}USAGES case
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.