6a3e14ac28
commit 67ab51cbdfee02ef07fb9d7d14cc0bf6cb5a5e5c upstream. Commit18011eac28("arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks") tried to optimise the context switching of tpidrro_el0 by eliding the clearing of the register when switching to a native task with kpti enabled, on the erroneous assumption that the kpti trampoline entry code would already have taken care of the write. Although the kpti trampoline does zero the register on entry from a native task, the check in tls_thread_switch() is on the *next* task and so we can end up leaving a stale, non-zero value in the register if the previous task was 32-bit. Drop the broken optimisation and zero tpidrro_el0 unconditionally when switching to a native 64-bit task. Cc: Mark Rutland <mark.rutland@arm.com> Cc: stable@vger.kernel.org Fixes:18011eac28("arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks") Signed-off-by: Will Deacon <will@kernel.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20241114095332.23391-1-will@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.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.
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.