[PATCH RESEND v2 0/2] riscv: Fix set_memory_XX() and set_direct_map_XX()

From: Alexandre Ghiti <alexghiti@rivosinc.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Mike Rapoport <rppt@kernel.org>,
	linux-mm@kvack.org, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Subject: [PATCH RESEND v2 0/2] riscv: Fix set_memory_XX() and set_direct_map_XX()
Date: Wed,  8 Nov 2023 08:59:28 +0100	[thread overview]
Message-ID: <20231108075930.7157-1-alexghiti@rivosinc.com> (raw)

Those 2 patches fix the set_memory_XX() and set_direct_map_XX() APIs, which
in turn fix STRICT_KERNEL_RWX and memfd_secret(). Those were broken since the
permission changes were not applied to the linear mapping because the linear
mapping is mapped using hugepages and walk_page_range_novma() does not split
such mappings.

To fix that, patch 1 disables PGD mappings in the linear mapping as it is
hard to propagate changes at this level in *all* the page tables, this has the
downside of disabling PMD mapping for sv32 and PUD (1GB) mapping for sv39 in
the linear mapping (for specific kernels, we could add a Kconfig to enable
ARCH_HAS_SET_DIRECT_MAP and STRICT_KERNEL_RWX if needed, I'm pretty sure we'll
discuss that).

patch 2 implements the split of the huge linear mappings so that
walk_page_range_novma() can properly apply the permissions. The whole split is
protected with mmap_sem in write mode, but I'm wondering if that's enough,
any opinion on that is appreciated.

Changes in v2:
- Fix rv32 build
- Rebase on top of 6.6-rc6
- Move the flush_tlb_all outside the mmap_lock

Alexandre Ghiti (2):
  riscv: Don't use PGD entries for the linear mapping
  riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge
    linear mappings

 arch/riscv/mm/init.c     |  12 +-
 arch/riscv/mm/pageattr.c | 270 +++++++++++++++++++++++++++++++++------
 2 files changed, 236 insertions(+), 46 deletions(-)

-- 
2.39.2