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[ Upstream commit912efa17e5] Since commit0758cd8304("asm-generic/tlb: avoid potential double flush"), TLB invalidation is elided in tlb_finish_mmu() if no entries were batched via the tlb_remove_*() functions. Consequently, the page-table modifications performed by clear_refs_write() in response to a write to /proc/<pid>/clear_refs do not perform TLB invalidation. Although this is fine when simply aging the ptes, in the case of clearing the "soft-dirty" state we can end up with entries where pte_write() is false, yet a writable mapping remains in the TLB. Fix this by avoiding the mmu_gather API altogether: managing both the 'tlb_flush_pending' flag on the 'mm_struct' and explicit TLB invalidation for the sort-dirty path, much like mprotect() does already. Fixes:0758cd8304("asm-generic/tlb: avoid potential double flush”) Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Yu Zhao <yuzhao@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lkml.kernel.org/r/20210127235347.1402-2-will@kernel.org 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.