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[ Upstream commitf35d2f249e] copy-paste contains implicit "copy buffer" state that can contain arbitrary user data (if the user process executes a copy instruction). This could be snooped by another process if a context switch hits while the state is live. So cp_abort is executed on context switch to clear out possible sensitive data and prevent the leak. cp_abort is done after the low level _switch(), which means it is never reached by newly created tasks, so they could snoop on this buffer between their first and second context switch. Fix this by doing the cp_abort before calling _switch. Add some comments which should make the issue harder to miss. Fixes:07d2a628bc("powerpc/64s: Avoid cpabort in context switch when possible") Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210622053036.474678-1-npiggin@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.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.