From: Patrick Roy roypat@amazon.co.uk
Use the new per-module export functionality to allow KVM (and only KVM) access to set_direct_map_valid_noflush(). This allows guest_memfd to remove its memory from the direct map, even if KVM is built as a module.
Direct map removal gives guest_memfd the same protection that memfd_secret enjoys, such as hardening against Spectre-like attacks through in-kernel gadgets.
Cc: linux-arm-kernel@lists.infradead.org Cc: loongarch@lists.linux.dev Cc: linux-riscv@lists.infradead.org Cc: linux-s390@vger.kernel.org Reviewed-by: Fuad Tabba tabba@google.com Signed-off-by: Patrick Roy roypat@amazon.co.uk --- arch/arm64/mm/pageattr.c | 1 + arch/loongarch/mm/pageattr.c | 1 + arch/riscv/mm/pageattr.c | 1 + arch/s390/mm/pageattr.c | 1 + arch/x86/mm/pat/set_memory.c | 1 + 5 files changed, 5 insertions(+)
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 04d4a8f676db..4f3cddfab9b0 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -291,6 +291,7 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
return set_memory_valid(addr, nr, valid); } +EXPORT_SYMBOL_FOR_MODULES(set_direct_map_valid_noflush, "kvm");
#ifdef CONFIG_DEBUG_PAGEALLOC /* diff --git a/arch/loongarch/mm/pageattr.c b/arch/loongarch/mm/pageattr.c index f5e910b68229..458f5ae6a89b 100644 --- a/arch/loongarch/mm/pageattr.c +++ b/arch/loongarch/mm/pageattr.c @@ -236,3 +236,4 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
return __set_memory(addr, 1, set, clear); } +EXPORT_SYMBOL_FOR_MODULES(set_direct_map_valid_noflush, "kvm"); diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c index 3f76db3d2769..6db31040cd66 100644 --- a/arch/riscv/mm/pageattr.c +++ b/arch/riscv/mm/pageattr.c @@ -400,6 +400,7 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
return __set_memory((unsigned long)page_address(page), nr, set, clear); } +EXPORT_SYMBOL_FOR_MODULES(set_direct_map_valid_noflush, "kvm");
#ifdef CONFIG_DEBUG_PAGEALLOC static int debug_pagealloc_set_page(pte_t *pte, unsigned long addr, void *data) diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c index 348e759840e7..8ffd9ef09bc6 100644 --- a/arch/s390/mm/pageattr.c +++ b/arch/s390/mm/pageattr.c @@ -413,6 +413,7 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
return __set_memory((unsigned long)page_to_virt(page), nr, flags); } +EXPORT_SYMBOL_FOR_MODULES(set_direct_map_valid_noflush, "kvm");
bool kernel_page_present(struct page *page) { diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 8834c76f91c9..87e9c7d2dcdc 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -2661,6 +2661,7 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
return __set_pages_np(page, nr); } +EXPORT_SYMBOL_FOR_MODULES(set_direct_map_valid_noflush, "kvm");
#ifdef CONFIG_DEBUG_PAGEALLOC void __kernel_map_pages(struct page *page, int numpages, int enable)