| Message ID | 20231108075930.7157-1-alexghiti@rivosinc.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | riscv: Fix set_memory_XX() and set_direct_map_XX() | expand |
Hello: This series was applied to riscv/linux.git (for-next) by Palmer Dabbelt <palmer@rivosinc.com>: On Wed, 8 Nov 2023 08:59:28 +0100 you wrote: > 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). > > [...] Here is the summary with links: - [RESEND,v2,1/2] riscv: Don't use PGD entries for the linear mapping https://git.kernel.org/riscv/c/629db01c64ff - [RESEND,v2,2/2] riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge linear mappings https://git.kernel.org/riscv/c/311cd2f6e253 You are awesome, thank you!
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(-)