dd7ef7bd14
In a low-memory situation, cc->fast_search_fail can keep increasing as it is unable to find an available page to isolate in fast_isolate_freepages(). As the result, it could trigger an error below, so just compare with the maximum bits can be shifted first. UBSAN: Undefined behaviour in mm/compaction.c:1160:30 shift exponent 64 is too large for 64-bit type 'unsigned long' CPU: 131 PID: 1308 Comm: kcompactd1 Kdump: loaded Tainted: G W L 5.0.0+ #17 Call trace: dump_backtrace+0x0/0x450 show_stack+0x20/0x2c dump_stack+0xc8/0x14c __ubsan_handle_shift_out_of_bounds+0x7e8/0x8c4 compaction_alloc+0x2344/0x2484 unmap_and_move+0xdc/0x1dbc migrate_pages+0x274/0x1310 compact_zone+0x26ec/0x43bc kcompactd+0x15b8/0x1a24 kthread+0x374/0x390 ret_from_fork+0x10/0x18 [akpm@linux-foundation.org: code cleanup] Link: http://lkml.kernel.org/r/20190320203338.53367-1-cai@lca.pw Fixes: 70b44595eafe ("mm, compaction: use free lists to quickly locate a migration source") Signed-off-by: Qian Cai <cai@lca.pw> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.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.
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.