f98b6215d7
Although we have start, len check for extent buffer reader/write (e.g. read_extent_buffer()), these checks have limitations: - No overflow check Values like start = 1024 len = -1024 can still pass the basic (start + len) > eb->len check. - Checks are not consistent For read_extent_buffer() we only check (start + len) against eb->len. While for memcmp_extent_buffer() we also check start against eb->len. - Different error reporting mechanism We use WARN() in read_extent_buffer() but BUG() in memcpy_extent_buffer(). - Still modify memory if the request is obviously wrong In read_extent_buffer() even we find (start + len) > eb->len, we still call memset(dst, 0, len), which can easily cause memory access error if start + len overflows. To address above problems, this patch creates a new common function to check such access, check_eb_range(). - Add overflow check This function checks start, start + len against eb->len and overflow check. - Unified checks - Unified error reports Will call WARN() if CONFIG_BTRFS_DEBUG is configured. And also do btrfs_warn() message for non-debug build. - Exit ASAP if check fails No more possible memory corruption. - Add extra comment for @start @len used in those functions as it's sometimes confused with the logical addressing instead of a range inside the eb space Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202817 [ Inspired by above report, the report itself is already addressed ] Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> [ use check_add_overflow ] Signed-off-by: David Sterba <dsterba@suse.com>
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.