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[ Upstream commit f3554aeb99 ]
This fixes a divide by zero error in the setup_format_params function of
the floppy driver.
Two consecutive ioctls can trigger the bug: The first one should set the
drive geometry with such .sect and .rate values for the F_SECT_PER_TRACK
to become zero. Next, the floppy format operation should be called.
A floppy disk is not required to be inserted. An unprivileged user
could trigger the bug if the device is accessible.
The patch checks F_SECT_PER_TRACK for a non-zero value in the
set_geometry function. The proper check should involve a reasonable
upper limit for the .sect and .rate fields, but it could change the
UAPI.
The patch also checks F_SECT_PER_TRACK in the setup_format_params, and
cancels the formatting operation in case of zero.
The bug was found by syzkaller.
Signed-off-by: Denis Efremov <efremov@ispras.ru>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.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.