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There is a corner case that slips through the checkers in functions reading extent buffer, ie. if (start < eb->len) and (start + len > eb->len), then a) map_private_extent_buffer() returns immediately because it's thinking the range spans across two pages, b) and the checkers in read_extent_buffer(), WARN_ON(start > eb->len) and WARN_ON(start + len > eb->start + eb->len), both are OK in this corner case, but it'd actually try to access the eb->pages out of bounds because of (start + len > eb->len). The case is found by switching extent inline ref type from shared data ref to non-shared data ref, which is a kind of metadata corruption. It'd use the wrong helper to access the eb, eg. btrfs_extent_data_ref_root(eb, ref) is used but the %ref passing here is "struct btrfs_shared_data_ref". And if the extent item happens to be the first item in the eb, then offset/length will get over eb->len which ends up an invalid memory access. This is adding proper checks in order to avoid invalid memory access, ie. 'general protection fault', before it's too late. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: Chris Mason <clm@fb.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.