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49c2ef075d
commit 68f6bd128e75a032432eda9d16676ed2969a1096 upstream.
When reading a compressed file, we may read several pages in addition to
the one requested. The current code will overwrite pages in the page
cache with the data from disc which can definitely result in changes
that have been made being lost.
For example if we have four consecutie pages ABCD in the file compressed
into a single extent, on first access, we'll bring in ABCD. Then we
write to page B. Memory pressure results in the eviction of ACD.
When we attempt to write to page C, we will overwrite the data in page
B with the data currently on disk.
I haven't investigated the decompression code to check whether it's
OK to overwrite a clean page or whether it might be possible to see
corrupt data. Out of an abundance of caution, decline to overwrite
uptodate pages, not just dirty pages.
Fixes: 4342306f0f (fs/ntfs3: Add file operations and implementation)
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.