[PATCH v5 16/23] powerpc/book3s64/kuap: Restrict access to userspace based on userspace AMR
From: Aneesh Kumar K.V <hidden>
Date: 2020-08-27 04:42:29
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
If an application has configured address protection such that read/write is denied using pkey even the kernel should receive a FAULT on accessing the same. This patch use user AMR value stored in pt_regs.kuap to achieve the same. Signed-off-by: Aneesh Kumar K.V <redacted> --- arch/powerpc/include/asm/book3s/64/kup.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h
index 4e1d666032f6..878cd84922d8 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h@@ -292,14 +292,20 @@ static inline void set_kuap(unsigned long value) static __always_inline void allow_user_access(void __user *to, const void __user *from, unsigned long size, unsigned long dir) { + unsigned long thread_amr = 0; + // This is written so we can resolve to a single case at build time BUILD_BUG_ON(!__builtin_constant_p(dir)); + + if (mmu_has_feature(MMU_FTR_PKEY)) + thread_amr = current_thread_amr(); + if (dir == KUAP_READ) - set_kuap(AMR_KUAP_BLOCK_WRITE); + set_kuap(thread_amr | AMR_KUAP_BLOCK_WRITE); else if (dir == KUAP_WRITE) - set_kuap(AMR_KUAP_BLOCK_READ); + set_kuap(thread_amr | AMR_KUAP_BLOCK_READ); else if (dir == KUAP_READ_WRITE) - set_kuap(0); + set_kuap(thread_amr); else BUILD_BUG(); }
--
2.26.2