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commit d28c756cae upstream.
The zero-copy optimization when reading or writing large chunks of data
is quite useful. However, the 9p messages created through the zero-copy
write path have an incorrect message size: it should be the size of the
header + size of the data being written but instead it's just the size
of the header.
This only works if the server ignores the size field of the message and
otherwise breaks the framing of the protocol. Fix this by re-writing the
message size field with the correct value.
Tested by running `dd if=/dev/zero of=out bs=4k count=1` inside a
virtio-9p mount.
Link: http://lkml.kernel.org/r/20180717003529.114368-1-chirantan@chromium.org
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>
Cc: Dylan Reid <dgreid@chromium.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.