CVE-2015-0275 -- Linux kernel: fs: ext4: fallocate zero range page size > block size BUG()

[Petr Matousek <pmatouse () redhat com>]

Currently there is a bug in zero range code which causes zero range
calls to only allocate block aligned portion of the range, while
ignoring the rest in some cases.

In some cases, namely if the end of the range is past isize, we do
attempt to preallocate the last nonaligned block. However this might
cause kernel to BUG() in some carefully designed zero range requests on
setups where page size > block size.

Proposed upstream patch:
http://www.spinics.net/lists/linux-ext4/msg47193.html

References:
https://bugzilla.redhat.com/show_bug.cgi?id=1193907

Thanks,
-- 
Petr Matousek / Red Hat Product Security
PGP: 0xC44977CA 8107 AF16 A416 F9AF 18F3  D874 3E78 6F42 C449 77CA