[PATCH v20 0/7] mm: introduce memfd_secret system call to create "secret" memory areas

[PATCH v20 0/7] mm: introduce memfd_secret system call to create "secret" memory areas

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

Hi,

@Andrew, this is based on v5.13-rc1, I can rebase whatever way you prefer.

This is an implementation of "secret" mappings backed by a file descriptor.

The file descriptor backing secret memory mappings is created using a
dedicated memfd_secret system call The desired protection mode for the
memory is configured using flags parameter of the system call. The mmap()
of the file descriptor created with memfd_secret() will create a "secret"
memory mapping. The pages in that mapping will be marked as not present in
the direct map and will be present only in the page table of the owning mm.

Although normally Linux userspace mappings are protected from other users,
such secret mappings are useful for environments where a hostile tenant is
trying to trick the kernel into giving them access to other tenants
mappings.

It's designed to provide the following protections:

* Enhanced protection (in conjunction with all the other in-kernel
attack prevention systems) against ROP attacks. Seceretmem makes "simple"
ROP insufficient to perform exfiltration, which increases the required
complexity of the attack. Along with other protections like the kernel
stack size limit and address space layout randomization which make finding
gadgets is really hard, absence of any in-kernel primitive for accessing
secret memory means the one gadget ROP attack can't work. Since the only
way to access secret memory is to reconstruct the missing mapping entry,
the attacker has to recover the physical page and insert a PTE pointing to
it in the kernel and then retrieve the contents.  That takes at least three
gadgets which is a level of difficulty beyond most standard attacks.

* Prevent cross-process secret userspace memory exposures. Once the secret
memory is allocated, the user can't accidentally pass it into the kernel to
be transmitted somewhere. The secreremem pages cannot be accessed via the
direct map and they are disallowed in GUP.

* Harden against exploited kernel flaws. In order to access secretmem, a
kernel-side attack would need to either walk the page tables and create new
ones, or spawn a new privileged uiserspace process to perform secrets
exfiltration using ptrace.

In the future the secret mappings may be used as a mean to protect guest memory
in a virtual machine host.

For demonstration of secret memory usage we've created a userspace library

https://git.kernel.org/pub/scm/linux/kernel/git/jejb/secret-memory-preloader.git

that does two things: the first is act as a preloader for openssl to
redirect all the OPENSSL_malloc calls to secret memory meaning any secret
keys get automatically protected this way and the other thing it does is
expose the API to the user who needs it. We anticipate that a lot of the
use cases would be like the openssl one: many toolkits that deal with
secret keys already have special handling for the memory to try to give
them greater protection, so this would simply be pluggable into the
toolkits without any need for user application modification.

Hiding secret memory mappings behind an anonymous file allows usage of
the page cache for tracking pages allocated for the "secret" mappings as
well as using address_space_operations for e.g. page migration callbacks.

The anonymous file may be also used implicitly, like hugetlb files, to
implement mmap(MAP_SECRET) and use the secret memory areas with "native" mm
ABIs in the future.

Removing of the pages from the direct map may cause its fragmentation on
architectures that use large pages to map the physical memory which affects
the system performance. However, the original Kconfig text for
CONFIG_DIRECT_GBPAGES said that gigabyte pages in the direct map "... can
improve the kernel's performance a tiny bit ..." (commit 00d1c5e05736
("x86: add gbpages switches")) and the recent report [1] showed that "...
although 1G mappings are a good default choice, there is no compelling
evidence that it must be the only choice". Hence, it is sufficient to have
secretmem disabled by default with the ability of a system administrator to
enable it at boot time.

In addition, there is also a long term goal to improve management of the
direct map.

[1] https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/

v20:
* Drop the patch that enable multi-page updates to the direct map, per David
* Drop the changes to /dev/mem, they anyway have no effect when CONFIG_STRICT_DEVMEM=y
* Add Acked-by and Reviewed-by tags

v19: https://lore.kernel.org/lkml/20210513184734.29317-1-rppt@kernel.org
* block /dev/mem mmap access, per David
* disallow mmap/mprotect with PROT_EXEC, per Kees
* simplify return in page_is_secretmem(), per Matthew
* use unsigned int for syscall falgs, per Yury

v18: https://lore.kernel.org/lkml/20210303162209.8609-1-rppt@kernel.org
* rebase on v5.12-rc1
* merge kfence fix into the original patch
* massage commit message of the patch introducing the memfd_secret syscall

v17: https://lore.kernel.org/lkml/20210208084920.2884-1-rppt@kernel.org
* Remove pool of large pages backing secretmem allocations, per Michal Hocko
* Add secretmem pages to unevictable LRU, per Michal Hocko
* Use GFP_HIGHUSER as secretmem mapping mask, per Michal Hocko
* Make secretmem an opt-in feature that is disabled by default
 
v16: https://lore.kernel.org/lkml/20210121122723.3446-1-rppt@kernel.org
* Fix memory leak intorduced in v15
* Clean the data left from previous page user before handing the page to
  the userspace

Older history:
v15: https://lore.kernel.org/lkml/20210120180612.1058-1-rppt@kernel.org
v14: https://lore.kernel.org/lkml/20201203062949.5484-1-rppt@kernel.org
v13: https://lore.kernel.org/lkml/20201201074559.27742-1-rppt@kernel.org
v12: https://lore.kernel.org/lkml/20201125092208.12544-1-rppt@kernel.org
v11: https://lore.kernel.org/lkml/20201124092556.12009-1-rppt@kernel.org
v10: https://lore.kernel.org/lkml/20201123095432.5860-1-rppt@kernel.org
v9: https://lore.kernel.org/lkml/20201117162932.13649-1-rppt@kernel.org
v8: https://lore.kernel.org/lkml/20201110151444.20662-1-rppt@kernel.org
v7: https://lore.kernel.org/lkml/20201026083752.13267-1-rppt@kernel.org
v6: https://lore.kernel.org/lkml/20200924132904.1391-1-rppt@kernel.org
v5: https://lore.kernel.org/lkml/20200916073539.3552-1-rppt@kernel.org
v4: https://lore.kernel.org/lkml/20200818141554.13945-1-rppt@kernel.org
v3: https://lore.kernel.org/lkml/20200804095035.18778-1-rppt@kernel.org
v2: https://lore.kernel.org/lkml/20200727162935.31714-1-rppt@kernel.org
v1: https://lore.kernel.org/lkml/20200720092435.17469-1-rppt@kernel.org
rfc-v2: https://lore.kernel.org/lkml/20200706172051.19465-1-rppt@kernel.org/
rfc-v1: https://lore.kernel.org/lkml/20200130162340.GA14232@rapoport-lnx/
rfc-v0: https://lore.kernel.org/lkml/1572171452-7958-1-git-send-email-rppt@kernel.org/

Mike Rapoport (7):
  mmap: make mlock_future_check() global
  riscv/Kconfig: make direct map manipulation options depend on MMU
  set_memory: allow querying whether set_direct_map_*() is actually
    enabled
  mm: introduce memfd_secret system call to create "secret" memory areas
  PM: hibernate: disable when there are active secretmem users
  arch, mm: wire up memfd_secret system call where relevant
  secretmem: test: add basic selftest for memfd_secret(2)

 arch/arm64/include/asm/Kbuild             |   1 -
 arch/arm64/include/asm/cacheflush.h       |   6 -
 arch/arm64/include/asm/kfence.h           |   2 +-
 arch/arm64/include/asm/set_memory.h       |  17 ++
 arch/arm64/include/uapi/asm/unistd.h      |   1 +
 arch/arm64/kernel/machine_kexec.c         |   1 +
 arch/arm64/mm/mmu.c                       |   6 +-
 arch/arm64/mm/pageattr.c                  |  13 +-
 arch/riscv/Kconfig                        |   4 +-
 arch/riscv/include/asm/unistd.h           |   1 +
 arch/x86/entry/syscalls/syscall_32.tbl    |   1 +
 arch/x86/entry/syscalls/syscall_64.tbl    |   1 +
 include/linux/secretmem.h                 |  54 ++++
 include/linux/set_memory.h                |  12 +
 include/linux/syscalls.h                  |   1 +
 include/uapi/asm-generic/unistd.h         |   7 +-
 include/uapi/linux/magic.h                |   1 +
 kernel/power/hibernate.c                  |   5 +-
 kernel/sys_ni.c                           |   2 +
 mm/Kconfig                                |   5 +
 mm/Makefile                               |   1 +
 mm/gup.c                                  |  12 +
 mm/internal.h                             |   3 +
 mm/mlock.c                                |   3 +-
 mm/mmap.c                                 |   5 +-
 mm/secretmem.c                            | 254 +++++++++++++++++++
 scripts/checksyscalls.sh                  |   4 +
 tools/testing/selftests/vm/.gitignore     |   1 +
 tools/testing/selftests/vm/Makefile       |   3 +-
 tools/testing/selftests/vm/memfd_secret.c | 296 ++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests.sh |  17 ++
 31 files changed, 716 insertions(+), 24 deletions(-)
 create mode 100644 arch/arm64/include/asm/set_memory.h
 create mode 100644 include/linux/secretmem.h
 create mode 100644 mm/secretmem.c
 create mode 100644 tools/testing/selftests/vm/memfd_secret.c


base-commit: 6efb943b8616ec53a5e444193dccf1af9ad627b5
-- 
2.28.0


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[PATCH v20 1/7] mmap: make mlock_future_check() global

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

It will be used by the upcoming secret memory implementation.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
---
 mm/internal.h | 3 +++
 mm/mmap.c     | 5 ++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 54bd0dc2c23c..46eb82eaa195 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -373,6 +373,9 @@ static inline void munlock_vma_pages_all(struct vm_area_struct *vma)
 extern void mlock_vma_page(struct page *page);
 extern unsigned int munlock_vma_page(struct page *page);
 
+extern int mlock_future_check(struct mm_struct *mm, unsigned long flags,
+			      unsigned long len);
+
 /*
  * Clear the page's PageMlocked().  This can be useful in a situation where
  * we want to unconditionally remove a page from the pagecache -- e.g.,
diff --git a/mm/mmap.c b/mm/mmap.c
index 0584e540246e..81f5595a8490 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1352,9 +1352,8 @@ static inline unsigned long round_hint_to_min(unsigned long hint)
 	return hint;
 }
 
-static inline int mlock_future_check(struct mm_struct *mm,
-				     unsigned long flags,
-				     unsigned long len)
+int mlock_future_check(struct mm_struct *mm, unsigned long flags,
+		       unsigned long len)
 {
 	unsigned long locked, lock_limit;
 
-- 
2.28.0


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[PATCH v20 2/7] riscv/Kconfig: make direct map manipulation options depend on MMU

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

ARCH_HAS_SET_DIRECT_MAP and ARCH_HAS_SET_MEMORY configuration options have
no meaning when CONFIG_MMU is disabled and there is no point to enable
them for the nommu case.

Add an explicit dependency on MMU for these options.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 arch/riscv/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a8ad8eb76120..c426e7d20907 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -26,8 +26,8 @@ config RISCV
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_MMIOWB
 	select ARCH_HAS_PTE_SPECIAL
-	select ARCH_HAS_SET_DIRECT_MAP
-	select ARCH_HAS_SET_MEMORY
+	select ARCH_HAS_SET_DIRECT_MAP if MMU
+	select ARCH_HAS_SET_MEMORY if MMU
 	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
 	select ARCH_HAS_STRICT_MODULE_RWX if MMU && !XIP_KERNEL
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
-- 
2.28.0


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[PATCH v20 3/7] set_memory: allow querying whether set_direct_map_*() is actually enabled

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

On arm64, set_direct_map_*() functions may return 0 without actually
changing the linear map.  This behaviour can be controlled using kernel
parameters, so we need a way to determine at runtime whether calls to
set_direct_map_invalid_noflush() and set_direct_map_default_noflush() have
any effect.

Extend set_memory API with can_set_direct_map() function that allows
checking if calling set_direct_map_*() will actually change the page
table, replace several occurrences of open coded checks in arm64 with the
new function and provide a generic stub for architectures that always
modify page tables upon calls to set_direct_map APIs.

[arnd@arndb.de: arm64: kfence: fix header inclusion ]

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/Kbuild       |  1 -
 arch/arm64/include/asm/cacheflush.h |  6 ------
 arch/arm64/include/asm/kfence.h     |  2 +-
 arch/arm64/include/asm/set_memory.h | 17 +++++++++++++++++
 arch/arm64/kernel/machine_kexec.c   |  1 +
 arch/arm64/mm/mmu.c                 |  6 +++---
 arch/arm64/mm/pageattr.c            | 13 +++++++++----
 include/linux/set_memory.h          | 12 ++++++++++++
 8 files changed, 43 insertions(+), 15 deletions(-)
 create mode 100644 arch/arm64/include/asm/set_memory.h

diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
index 07ac208edc89..73aa25843f65 100644
--- a/arch/arm64/include/asm/Kbuild
+++ b/arch/arm64/include/asm/Kbuild
@@ -3,5 +3,4 @@ generic-y += early_ioremap.h
 generic-y += mcs_spinlock.h
 generic-y += qrwlock.h
 generic-y += qspinlock.h
-generic-y += set_memory.h
 generic-y += user.h
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index 52e5c1623224..4e3c13799735 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -131,12 +131,6 @@ static __always_inline void __flush_icache_all(void)
 	dsb(ish);
 }
 
-int set_memory_valid(unsigned long addr, int numpages, int enable);
-
-int set_direct_map_invalid_noflush(struct page *page);
-int set_direct_map_default_noflush(struct page *page);
-bool kernel_page_present(struct page *page);
-
 #include <asm-generic/cacheflush.h>
 
 #endif /* __ASM_CACHEFLUSH_H */
diff --git a/arch/arm64/include/asm/kfence.h b/arch/arm64/include/asm/kfence.h
index d061176d57ea..aa855c6a0ae6 100644
--- a/arch/arm64/include/asm/kfence.h
+++ b/arch/arm64/include/asm/kfence.h
@@ -8,7 +8,7 @@
 #ifndef __ASM_KFENCE_H
 #define __ASM_KFENCE_H
 
-#include <asm/cacheflush.h>
+#include <asm/set_memory.h>
 
 static inline bool arch_kfence_init_pool(void) { return true; }
 
diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h
new file mode 100644
index 000000000000..0f740b781187
--- /dev/null
+++ b/arch/arm64/include/asm/set_memory.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _ASM_ARM64_SET_MEMORY_H
+#define _ASM_ARM64_SET_MEMORY_H
+
+#include <asm-generic/set_memory.h>
+
+bool can_set_direct_map(void);
+#define can_set_direct_map can_set_direct_map
+
+int set_memory_valid(unsigned long addr, int numpages, int enable);
+
+int set_direct_map_invalid_noflush(struct page *page);
+int set_direct_map_default_noflush(struct page *page);
+bool kernel_page_present(struct page *page);
+
+#endif /* _ASM_ARM64_SET_MEMORY_H */
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 90a335c74442..0ec94e718724 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/kexec.h>
 #include <linux/page-flags.h>
+#include <linux/set_memory.h>
 #include <linux/smp.h>
 
 #include <asm/cacheflush.h>
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 6dd9369e3ea0..e42aeff6c344 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -22,6 +22,7 @@
 #include <linux/io.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
+#include <linux/set_memory.h>
 
 #include <asm/barrier.h>
 #include <asm/cputype.h>
@@ -515,7 +516,7 @@ static void __init map_mem(pgd_t *pgdp)
 	 */
 	BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end));
 
-	if (rodata_full || crash_mem_map || debug_pagealloc_enabled())
+	if (can_set_direct_map() || crash_mem_map)
 		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 	/*
@@ -1483,8 +1484,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
 	 * KFENCE requires linear map to be mapped at page granularity, so that
 	 * it is possible to protect/unprotect single pages in the KFENCE pool.
 	 */
-	if (rodata_full || debug_pagealloc_enabled() ||
-	    IS_ENABLED(CONFIG_KFENCE))
+	if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
 		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 	__create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 92eccaf595c8..a3bacd79507a 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -19,6 +19,11 @@ struct page_change_data {
 
 bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
 
+bool can_set_direct_map(void)
+{
+	return rodata_full || debug_pagealloc_enabled();
+}
+
 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
 {
 	struct page_change_data *cdata = data;
@@ -155,7 +160,7 @@ int set_direct_map_invalid_noflush(struct page *page)
 		.clear_mask = __pgprot(PTE_VALID),
 	};
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return 0;
 
 	return apply_to_page_range(&init_mm,
@@ -170,7 +175,7 @@ int set_direct_map_default_noflush(struct page *page)
 		.clear_mask = __pgprot(PTE_RDONLY),
 	};
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return 0;
 
 	return apply_to_page_range(&init_mm,
@@ -181,7 +186,7 @@ int set_direct_map_default_noflush(struct page *page)
 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return;
 
 	set_memory_valid((unsigned long)page_address(page), numpages, enable);
@@ -206,7 +211,7 @@ bool kernel_page_present(struct page *page)
 	pte_t *ptep;
 	unsigned long addr = (unsigned long)page_address(page);
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return true;
 
 	pgdp = pgd_offset_k(addr);
diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
index fe1aa4e54680..f36be5166c19 100644
--- a/include/linux/set_memory.h
+++ b/include/linux/set_memory.h
@@ -28,7 +28,19 @@ static inline bool kernel_page_present(struct page *page)
 {
 	return true;
 }
+#else /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
+/*
+ * Some architectures, e.g. ARM64 can disable direct map modifications at
+ * boot time. Let them overrive this query.
+ */
+#ifndef can_set_direct_map
+static inline bool can_set_direct_map(void)
+{
+	return true;
+}
+#define can_set_direct_map can_set_direct_map
 #endif
+#endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
 
 #ifndef set_mce_nospec
 static inline int set_mce_nospec(unsigned long pfn, bool unmap)
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v20 4/7] mm: introduce memfd_secret system call to create "secret" memory areas

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

Introduce "memfd_secret" system call with the ability to create memory
areas visible only in the context of the owning process and not mapped not
only to other processes but in the kernel page tables as well.

The secretmem feature is off by default and the user must explicitly enable
it at the boot time.

Once secretmem is enabled, the user will be able to create a file
descriptor using the memfd_secret() system call. The memory areas created
by mmap() calls from this file descriptor will be unmapped from the kernel
direct map and they will be only mapped in the page table of the processes
that have access to the file descriptor.

Secretmem is designed to provide the following protections:

* Enhanced protection (in conjunction with all the other in-kernel
attack prevention systems) against ROP attacks. Seceretmem makes "simple"
ROP insufficient to perform exfiltration, which increases the required
complexity of the attack. Along with other protections like the kernel
stack size limit and address space layout randomization which make finding
gadgets is really hard, absence of any in-kernel primitive for accessing
secret memory means the one gadget ROP attack can't work. Since the only
way to access secret memory is to reconstruct the missing mapping entry,
the attacker has to recover the physical page and insert a PTE pointing to
it in the kernel and then retrieve the contents.  That takes at least three
gadgets which is a level of difficulty beyond most standard attacks.

* Prevent cross-process secret userspace memory exposures. Once the secret
memory is allocated, the user can't accidentally pass it into the kernel to
be transmitted somewhere. The secreremem pages cannot be accessed via the
direct map and they are disallowed in GUP.

* Harden against exploited kernel flaws. In order to access secretmem, a
kernel-side attack would need to either walk the page tables and create new
ones, or spawn a new privileged uiserspace process to perform secrets
exfiltration using ptrace.

The file descriptor based memory has several advantages over the
"traditional" mm interfaces, such as mlock(), mprotect(), madvise(). File
descriptor approach allows explicit and controlled sharing of the memory
areas, it allows to seal the operations. Besides, file descriptor based
memory paves the way for VMMs to remove the secret memory range from the
userspace hipervisor process, for instance QEMU. Andy Lutomirski says:

  "Getting fd-backed memory into a guest will take some possibly major work
   in the kernel, but getting vma-backed memory into a guest without
   mapping it in the host user address space seems much, much worse."

memfd_secret() is made a dedicated system call rather than an extension to
memfd_create() because it's purpose is to allow the user to create more
secure memory mappings rather than to simply allow file based access to the
memory. Nowadays a new system call cost is negligible while it is way
simpler for userspace to deal with a clear-cut system calls than with a
multiplexer or an overloaded syscall. Moreover, the initial implementation
of memfd_secret() is completely distinct from memfd_create() so there is no
much sense in overloading memfd_create() to begin with. If there will be a
need for code sharing between these implementation it can be easily
achieved without a need to adjust user visible APIs.

The secret memory remains accessible in the process context using uaccess
primitives, but it is not exposed to the kernel otherwise; secret memory
areas are removed from the direct map and functions in the
follow_page()/get_user_page() family will refuse to return a page that
belongs to the secret memory area.

Once there will be a use case that will require exposing secretmem to the
kernel it will be an opt-in request in the system call flags so that user
would have to decide what data can be exposed to the kernel.

Removing of the pages from the direct map may cause its fragmentation on
architectures that use large pages to map the physical memory which affects
the system performance. However, the original Kconfig text for
CONFIG_DIRECT_GBPAGES said that gigabyte pages in the direct map "... can
improve the kernel's performance a tiny bit ..." (commit 00d1c5e05736
("x86: add gbpages switches")) and the recent report [1] showed that "...
although 1G mappings are a good default choice, there is no compelling
evidence that it must be the only choice". Hence, it is sufficient to have
secretmem disabled by default with the ability of a system administrator to
enable it at boot time.

Pages in the secretmem regions are unevictable and unmovable to avoid
accidental exposure of the sensitive data via swap or during page
migration.

Since the secretmem mappings are locked in memory they cannot exceed
RLIMIT_MEMLOCK. Since these mappings are already locked independently from
mlock(), an attempt to mlock()/munlock() secretmem range would fail and
mlockall()/munlockall() will ignore secretmem mappings.

However, unlike mlock()ed memory, secretmem currently behaves more like
long-term GUP: secretmem mappings are unmovable mappings directly consumed
by user space. With default limits, there is no excessive use of secretmem
and it poses no real problem in combination with ZONE_MOVABLE/CMA, but in
the future this should be addressed to allow balanced use of large amounts
of secretmem along with ZONE_MOVABLE/CMA.

A page that was a part of the secret memory area is cleared when it is
freed to ensure the data is not exposed to the next user of that page.

The following example demonstrates creation of a secret mapping (error
handling is omitted):

	fd = memfd_secret(0);
	ftruncate(fd, MAP_SIZE);
	ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
		   MAP_SHARED, fd, 0);

[1] https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Hagen Paul Pfeifer <hagen@jauu.net>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
---
 include/linux/secretmem.h  |  48 ++++++++
 include/uapi/linux/magic.h |   1 +
 kernel/sys_ni.c            |   2 +
 mm/Kconfig                 |   5 +
 mm/Makefile                |   1 +
 mm/gup.c                   |  12 ++
 mm/mlock.c                 |   3 +-
 mm/secretmem.c             | 239 +++++++++++++++++++++++++++++++++++++
 8 files changed, 310 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/secretmem.h
 create mode 100644 mm/secretmem.c

diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
new file mode 100644
index 000000000000..e617b4afcc62
--- /dev/null
+++ b/include/linux/secretmem.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _LINUX_SECRETMEM_H
+#define _LINUX_SECRETMEM_H
+
+#ifdef CONFIG_SECRETMEM
+
+extern const struct address_space_operations secretmem_aops;
+
+static inline bool page_is_secretmem(struct page *page)
+{
+	struct address_space *mapping;
+
+	/*
+	 * Using page_mapping() is quite slow because of the actual call
+	 * instruction and repeated compound_head(page) inside the
+	 * page_mapping() function.
+	 * We know that secretmem pages are not compound and LRU so we can
+	 * save a couple of cycles here.
+	 */
+	if (PageCompound(page) || !PageLRU(page))
+		return false;
+
+	mapping = (struct address_space *)
+		((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
+
+	if (mapping != page->mapping)
+		return false;
+
+	return mapping->a_ops == &secretmem_aops;
+}
+
+bool vma_is_secretmem(struct vm_area_struct *vma);
+
+#else
+
+static inline bool vma_is_secretmem(struct vm_area_struct *vma)
+{
+	return false;
+}
+
+static inline bool page_is_secretmem(struct page *page)
+{
+	return false;
+}
+
+#endif /* CONFIG_SECRETMEM */
+
+#endif /* _LINUX_SECRETMEM_H */
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index f3956fc11de6..35687dcb1a42 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -97,5 +97,6 @@
 #define DEVMEM_MAGIC		0x454d444d	/* "DMEM" */
 #define Z3FOLD_MAGIC		0x33
 #define PPC_CMM_MAGIC		0xc7571590
+#define SECRETMEM_MAGIC		0x5345434d	/* "SECM" */
 
 #endif /* __LINUX_MAGIC_H__ */
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 0ea8128468c3..4d7e377a74f3 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -358,6 +358,8 @@ COND_SYSCALL(pkey_mprotect);
 COND_SYSCALL(pkey_alloc);
 COND_SYSCALL(pkey_free);
 
+/* memfd_secret */
+COND_SYSCALL(memfd_secret);
 
 /*
  * Architecture specific weak syscall entries.
diff --git a/mm/Kconfig b/mm/Kconfig
index 02d44e3420f5..6d0972db7278 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -901,4 +901,9 @@ config KMAP_LOCAL
 # struct io_mapping based helper.  Selected by drivers that need them
 config IO_MAPPING
 	bool
+
+config SECRETMEM
+	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
+	select STRICT_DEVMEM
+
 endmenu
diff --git a/mm/Makefile b/mm/Makefile
index bf71e295e9f6..7bb6ed5e42e8 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -125,3 +125,4 @@ obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
 obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
 obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
 obj-$(CONFIG_IO_MAPPING) += io-mapping.o
+obj-$(CONFIG_SECRETMEM) += secretmem.o
diff --git a/mm/gup.c b/mm/gup.c
index 0697134b6a12..6515f82b0f32 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -10,6 +10,7 @@
 #include <linux/rmap.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
+#include <linux/secretmem.h>
 
 #include <linux/sched/signal.h>
 #include <linux/rwsem.h>
@@ -816,6 +817,9 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 	struct follow_page_context ctx = { NULL };
 	struct page *page;
 
+	if (vma_is_secretmem(vma))
+		return NULL;
+
 	page = follow_page_mask(vma, address, foll_flags, &ctx);
 	if (ctx.pgmap)
 		put_dev_pagemap(ctx.pgmap);
@@ -949,6 +953,9 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
 	if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
 		return -EOPNOTSUPP;
 
+	if (vma_is_secretmem(vma))
+		return -EFAULT;
+
 	if (write) {
 		if (!(vm_flags & VM_WRITE)) {
 			if (!(gup_flags & FOLL_FORCE))
@@ -2077,6 +2084,11 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 		if (!head)
 			goto pte_unmap;
 
+		if (unlikely(page_is_secretmem(page))) {
+			put_compound_head(head, 1, flags);
+			goto pte_unmap;
+		}
+
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
 			put_compound_head(head, 1, flags);
 			goto pte_unmap;
diff --git a/mm/mlock.c b/mm/mlock.c
index df590fda5688..5e9f4dea4e96 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -23,6 +23,7 @@
 #include <linux/hugetlb.h>
 #include <linux/memcontrol.h>
 #include <linux/mm_inline.h>
+#include <linux/secretmem.h>
 
 #include "internal.h"
 
@@ -503,7 +504,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 
 	if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
 	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
-	    vma_is_dax(vma))
+	    vma_is_dax(vma) || vma_is_secretmem(vma))
 		/* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
 		goto out;
 
diff --git a/mm/secretmem.c b/mm/secretmem.c
new file mode 100644
index 000000000000..972cd1bbc3cc
--- /dev/null
+++ b/mm/secretmem.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright IBM Corporation, 2021
+ *
+ * Author: Mike Rapoport <rppt@linux.ibm.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/swap.h>
+#include <linux/mount.h>
+#include <linux/memfd.h>
+#include <linux/bitops.h>
+#include <linux/printk.h>
+#include <linux/pagemap.h>
+#include <linux/syscalls.h>
+#include <linux/pseudo_fs.h>
+#include <linux/secretmem.h>
+#include <linux/set_memory.h>
+#include <linux/sched/signal.h>
+
+#include <uapi/linux/magic.h>
+
+#include <asm/tlbflush.h>
+
+#include "internal.h"
+
+#undef pr_fmt
+#define pr_fmt(fmt) "secretmem: " fmt
+
+/*
+ * Define mode and flag masks to allow validation of the system call
+ * parameters.
+ */
+#define SECRETMEM_MODE_MASK	(0x0)
+#define SECRETMEM_FLAGS_MASK	SECRETMEM_MODE_MASK
+
+static bool secretmem_enable __ro_after_init;
+module_param_named(enable, secretmem_enable, bool, 0400);
+MODULE_PARM_DESC(secretmem_enable,
+		 "Enable secretmem and memfd_secret(2) system call");
+
+static vm_fault_t secretmem_fault(struct vm_fault *vmf)
+{
+	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	pgoff_t offset = vmf->pgoff;
+	gfp_t gfp = vmf->gfp_mask;
+	unsigned long addr;
+	struct page *page;
+	int err;
+
+	if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
+		return vmf_error(-EINVAL);
+
+retry:
+	page = find_lock_page(mapping, offset);
+	if (!page) {
+		page = alloc_page(gfp | __GFP_ZERO);
+		if (!page)
+			return VM_FAULT_OOM;
+
+		err = set_direct_map_invalid_noflush(page);
+		if (err) {
+			put_page(page);
+			return vmf_error(err);
+		}
+
+		__SetPageUptodate(page);
+		err = add_to_page_cache_lru(page, mapping, offset, gfp);
+		if (unlikely(err)) {
+			put_page(page);
+			/*
+			 * If a split of large page was required, it
+			 * already happened when we marked the page invalid
+			 * which guarantees that this call won't fail
+			 */
+			set_direct_map_default_noflush(page);
+			if (err == -EEXIST)
+				goto retry;
+
+			return vmf_error(err);
+		}
+
+		addr = (unsigned long)page_address(page);
+		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+	}
+
+	vmf->page = page;
+	return VM_FAULT_LOCKED;
+}
+
+static const struct vm_operations_struct secretmem_vm_ops = {
+	.fault = secretmem_fault,
+};
+
+static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long len = vma->vm_end - vma->vm_start;
+
+	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
+		return -EINVAL;
+
+	if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len))
+		return -EAGAIN;
+
+	vma->vm_flags |= VM_LOCKED | VM_DONTDUMP;
+	vma->vm_ops = &secretmem_vm_ops;
+
+	return 0;
+}
+
+bool vma_is_secretmem(struct vm_area_struct *vma)
+{
+	return vma->vm_ops == &secretmem_vm_ops;
+}
+
+static const struct file_operations secretmem_fops = {
+	.mmap		= secretmem_mmap,
+};
+
+static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode)
+{
+	return false;
+}
+
+static int secretmem_migratepage(struct address_space *mapping,
+				 struct page *newpage, struct page *page,
+				 enum migrate_mode mode)
+{
+	return -EBUSY;
+}
+
+static void secretmem_freepage(struct page *page)
+{
+	set_direct_map_default_noflush(page);
+	clear_highpage(page);
+}
+
+const struct address_space_operations secretmem_aops = {
+	.freepage	= secretmem_freepage,
+	.migratepage	= secretmem_migratepage,
+	.isolate_page	= secretmem_isolate_page,
+};
+
+static struct vfsmount *secretmem_mnt;
+
+static struct file *secretmem_file_create(unsigned long flags)
+{
+	struct file *file = ERR_PTR(-ENOMEM);
+	struct inode *inode;
+
+	inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
+				 O_RDWR, &secretmem_fops);
+	if (IS_ERR(file))
+		goto err_free_inode;
+
+	mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+	mapping_set_unevictable(inode->i_mapping);
+
+	inode->i_mapping->a_ops = &secretmem_aops;
+
+	/* pretend we are a normal file with zero size */
+	inode->i_mode |= S_IFREG;
+	inode->i_size = 0;
+
+	return file;
+
+err_free_inode:
+	iput(inode);
+	return file;
+}
+
+SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
+{
+	struct file *file;
+	int fd, err;
+
+	/* make sure local flags do not confict with global fcntl.h */
+	BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC);
+
+	if (!secretmem_enable)
+		return -ENOSYS;
+
+	if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC))
+		return -EINVAL;
+
+	fd = get_unused_fd_flags(flags & O_CLOEXEC);
+	if (fd < 0)
+		return fd;
+
+	file = secretmem_file_create(flags);
+	if (IS_ERR(file)) {
+		err = PTR_ERR(file);
+		goto err_put_fd;
+	}
+
+	file->f_flags |= O_LARGEFILE;
+
+	fd_install(fd, file);
+	return fd;
+
+err_put_fd:
+	put_unused_fd(fd);
+	return err;
+}
+
+static int secretmem_init_fs_context(struct fs_context *fc)
+{
+	return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM;
+}
+
+static struct file_system_type secretmem_fs = {
+	.name		= "secretmem",
+	.init_fs_context = secretmem_init_fs_context,
+	.kill_sb	= kill_anon_super,
+};
+
+static int secretmem_init(void)
+{
+	int ret = 0;
+
+	if (!secretmem_enable)
+		return ret;
+
+	secretmem_mnt = kern_mount(&secretmem_fs);
+	if (IS_ERR(secretmem_mnt))
+		ret = PTR_ERR(secretmem_mnt);
+
+	/* prevent secretmem mappings from ever getting PROT_EXEC */
+	secretmem_mnt->mnt_flags |= MNT_NOEXEC;
+
+	return ret;
+}
+fs_initcall(secretmem_init);
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v20 5/7] PM: hibernate: disable when there are active secretmem users

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

It is unsafe to allow saving of secretmem areas to the hibernation
snapshot as they would be visible after the resume and this essentially
will defeat the purpose of secret memory mappings.

Prevent hibernation whenever there are active secret memory users.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
---
 include/linux/secretmem.h |  6 ++++++
 kernel/power/hibernate.c  |  5 ++++-
 mm/secretmem.c            | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
index e617b4afcc62..21c3771e6a56 100644
--- a/include/linux/secretmem.h
+++ b/include/linux/secretmem.h
@@ -30,6 +30,7 @@ static inline bool page_is_secretmem(struct page *page)
 }
 
 bool vma_is_secretmem(struct vm_area_struct *vma);
+bool secretmem_active(void);
 
 #else
 
@@ -43,6 +44,11 @@ static inline bool page_is_secretmem(struct page *page)
 	return false;
 }
 
+static inline bool secretmem_active(void)
+{
+	return false;
+}
+
 #endif /* CONFIG_SECRETMEM */
 
 #endif /* _LINUX_SECRETMEM_H */
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index da0b41914177..559acef3fddb 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -31,6 +31,7 @@
 #include <linux/genhd.h>
 #include <linux/ktime.h>
 #include <linux/security.h>
+#include <linux/secretmem.h>
 #include <trace/events/power.h>
 
 #include "power.h"
@@ -81,7 +82,9 @@ void hibernate_release(void)
 
 bool hibernation_available(void)
 {
-	return nohibernate == 0 && !security_locked_down(LOCKDOWN_HIBERNATION);
+	return nohibernate == 0 &&
+		!security_locked_down(LOCKDOWN_HIBERNATION) &&
+		!secretmem_active();
 }
 
 /**
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 972cd1bbc3cc..f77d25467a14 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -40,6 +40,13 @@ module_param_named(enable, secretmem_enable, bool, 0400);
 MODULE_PARM_DESC(secretmem_enable,
 		 "Enable secretmem and memfd_secret(2) system call");
 
+static atomic_t secretmem_users;
+
+bool secretmem_active(void)
+{
+	return !!atomic_read(&secretmem_users);
+}
+
 static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 {
 	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
@@ -94,6 +101,12 @@ static const struct vm_operations_struct secretmem_vm_ops = {
 	.fault = secretmem_fault,
 };
 
+static int secretmem_release(struct inode *inode, struct file *file)
+{
+	atomic_dec(&secretmem_users);
+	return 0;
+}
+
 static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	unsigned long len = vma->vm_end - vma->vm_start;
@@ -116,6 +129,7 @@ bool vma_is_secretmem(struct vm_area_struct *vma)
 }
 
 static const struct file_operations secretmem_fops = {
+	.release	= secretmem_release,
 	.mmap		= secretmem_mmap,
 };
 
@@ -202,6 +216,7 @@ SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
 	file->f_flags |= O_LARGEFILE;
 
 	fd_install(fd, file);
+	atomic_inc(&secretmem_users);
 	return fd;
 
 err_put_fd:
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v20 6/7] arch, mm: wire up memfd_secret system call where relevant

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

Wire up memfd_secret system call on architectures that define
ARCH_HAS_SET_DIRECT_MAP, namely arm64, risc-v and x86.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/include/uapi/asm/unistd.h   | 1 +
 arch/riscv/include/asm/unistd.h        | 1 +
 arch/x86/entry/syscalls/syscall_32.tbl | 1 +
 arch/x86/entry/syscalls/syscall_64.tbl | 1 +
 include/linux/syscalls.h               | 1 +
 include/uapi/asm-generic/unistd.h      | 7 ++++++-
 scripts/checksyscalls.sh               | 4 ++++
 7 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/uapi/asm/unistd.h b/arch/arm64/include/uapi/asm/unistd.h
index f83a70e07df8..ce2ee8f1e361 100644
--- a/arch/arm64/include/uapi/asm/unistd.h
+++ b/arch/arm64/include/uapi/asm/unistd.h
@@ -20,5 +20,6 @@
 #define __ARCH_WANT_SET_GET_RLIMIT
 #define __ARCH_WANT_TIME32_SYSCALLS
 #define __ARCH_WANT_SYS_CLONE3
+#define __ARCH_WANT_MEMFD_SECRET
 
 #include <asm-generic/unistd.h>
diff --git a/arch/riscv/include/asm/unistd.h b/arch/riscv/include/asm/unistd.h
index 977ee6181dab..6c316093a1e5 100644
--- a/arch/riscv/include/asm/unistd.h
+++ b/arch/riscv/include/asm/unistd.h
@@ -9,6 +9,7 @@
  */
 
 #define __ARCH_WANT_SYS_CLONE
+#define __ARCH_WANT_MEMFD_SECRET
 
 #include <uapi/asm/unistd.h>
 
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 28a1423ce32e..e44519020a43 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -451,3 +451,4 @@
 444	i386	landlock_create_ruleset	sys_landlock_create_ruleset
 445	i386	landlock_add_rule	sys_landlock_add_rule
 446	i386	landlock_restrict_self	sys_landlock_restrict_self
+447	i386	memfd_secret		sys_memfd_secret
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index ecd551b08d05..a06f16106f24 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -368,6 +368,7 @@
 444	common	landlock_create_ruleset	sys_landlock_create_ruleset
 445	common	landlock_add_rule	sys_landlock_add_rule
 446	common	landlock_restrict_self	sys_landlock_restrict_self
+447	common	memfd_secret		sys_memfd_secret
 
 #
 # Due to a historical design error, certain syscalls are numbered differently
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 050511e8f1f8..1a1b5d724497 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1050,6 +1050,7 @@ asmlinkage long sys_landlock_create_ruleset(const struct landlock_ruleset_attr _
 asmlinkage long sys_landlock_add_rule(int ruleset_fd, enum landlock_rule_type rule_type,
 		const void __user *rule_attr, __u32 flags);
 asmlinkage long sys_landlock_restrict_self(int ruleset_fd, __u32 flags);
+asmlinkage long sys_memfd_secret(unsigned int flags);
 
 /*
  * Architecture-specific system calls
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 6de5a7fc066b..28b388368cf6 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -873,8 +873,13 @@ __SYSCALL(__NR_landlock_add_rule, sys_landlock_add_rule)
 #define __NR_landlock_restrict_self 446
 __SYSCALL(__NR_landlock_restrict_self, sys_landlock_restrict_self)
 
+#ifdef __ARCH_WANT_MEMFD_SECRET
+#define __NR_memfd_secret 447
+__SYSCALL(__NR_memfd_secret, sys_memfd_secret)
+#endif
+
 #undef __NR_syscalls
-#define __NR_syscalls 447
+#define __NR_syscalls 448
 
 /*
  * 32 bit systems traditionally used different
diff --git a/scripts/checksyscalls.sh b/scripts/checksyscalls.sh
index a18b47695f55..b7609958ee36 100755
--- a/scripts/checksyscalls.sh
+++ b/scripts/checksyscalls.sh
@@ -40,6 +40,10 @@ cat << EOF
 #define __IGNORE_setrlimit	/* setrlimit */
 #endif
 
+#ifndef __ARCH_WANT_MEMFD_SECRET
+#define __IGNORE_memfd_secret
+#endif
+
 /* Missing flags argument */
 #define __IGNORE_renameat	/* renameat2 */
 
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v20 7/7] secretmem: test: add basic selftest for memfd_secret(2)

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

The test verifies that file descriptor created with memfd_secret does not
allow read/write operations, that secret memory mappings respect
RLIMIT_MEMLOCK and that remote accesses with process_vm_read() and
ptrace() to the secret memory fail.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
---
 tools/testing/selftests/vm/.gitignore     |   1 +
 tools/testing/selftests/vm/Makefile       |   3 +-
 tools/testing/selftests/vm/memfd_secret.c | 296 ++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests.sh |  17 ++
 4 files changed, 316 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/vm/memfd_secret.c

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index 1f651e85ed60..da92ded5a27c 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -21,5 +21,6 @@ va_128TBswitch
 map_fixed_noreplace
 write_to_hugetlbfs
 hmm-tests
+memfd_secret
 local_config.*
 split_huge_page_test
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 73e1cc96d7c2..266580ea938c 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -34,6 +34,7 @@ TEST_GEN_FILES += khugepaged
 TEST_GEN_FILES += map_fixed_noreplace
 TEST_GEN_FILES += map_hugetlb
 TEST_GEN_FILES += map_populate
+TEST_GEN_FILES += memfd_secret
 TEST_GEN_FILES += mlock-random-test
 TEST_GEN_FILES += mlock2-tests
 TEST_GEN_FILES += mremap_dontunmap
@@ -134,7 +135,7 @@ warn_32bit_failure:
 endif
 endif
 
-$(OUTPUT)/mlock-random-test: LDLIBS += -lcap
+$(OUTPUT)/mlock-random-test $(OUTPUT)/memfd_secret: LDLIBS += -lcap
 
 $(OUTPUT)/gup_test: ../../../../mm/gup_test.h
 
diff --git a/tools/testing/selftests/vm/memfd_secret.c b/tools/testing/selftests/vm/memfd_secret.c
new file mode 100644
index 000000000000..93e7e7ffed33
--- /dev/null
+++ b/tools/testing/selftests/vm/memfd_secret.c
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright IBM Corporation, 2021
+ *
+ * Author: Mike Rapoport <rppt@linux.ibm.com>
+ */
+
+#define _GNU_SOURCE
+#include <sys/uio.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/ptrace.h>
+#include <sys/syscall.h>
+#include <sys/resource.h>
+#include <sys/capability.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include "../kselftest.h"
+
+#define fail(fmt, ...) ksft_test_result_fail(fmt, ##__VA_ARGS__)
+#define pass(fmt, ...) ksft_test_result_pass(fmt, ##__VA_ARGS__)
+#define skip(fmt, ...) ksft_test_result_skip(fmt, ##__VA_ARGS__)
+
+#ifdef __NR_memfd_secret
+
+#define PATTERN	0x55
+
+static const int prot = PROT_READ | PROT_WRITE;
+static const int mode = MAP_SHARED;
+
+static unsigned long page_size;
+static unsigned long mlock_limit_cur;
+static unsigned long mlock_limit_max;
+
+static int memfd_secret(unsigned int flags)
+{
+	return syscall(__NR_memfd_secret, flags);
+}
+
+static void test_file_apis(int fd)
+{
+	char buf[64];
+
+	if ((read(fd, buf, sizeof(buf)) >= 0) ||
+	    (write(fd, buf, sizeof(buf)) >= 0) ||
+	    (pread(fd, buf, sizeof(buf), 0) >= 0) ||
+	    (pwrite(fd, buf, sizeof(buf), 0) >= 0))
+		fail("unexpected file IO\n");
+	else
+		pass("file IO is blocked as expected\n");
+}
+
+static void test_mlock_limit(int fd)
+{
+	size_t len;
+	char *mem;
+
+	len = mlock_limit_cur;
+	mem = mmap(NULL, len, prot, mode, fd, 0);
+	if (mem == MAP_FAILED) {
+		fail("unable to mmap secret memory\n");
+		return;
+	}
+	munmap(mem, len);
+
+	len = mlock_limit_max * 2;
+	mem = mmap(NULL, len, prot, mode, fd, 0);
+	if (mem != MAP_FAILED) {
+		fail("unexpected mlock limit violation\n");
+		munmap(mem, len);
+		return;
+	}
+
+	pass("mlock limit is respected\n");
+}
+
+static void try_process_vm_read(int fd, int pipefd[2])
+{
+	struct iovec liov, riov;
+	char buf[64];
+	char *mem;
+
+	if (read(pipefd[0], &mem, sizeof(mem)) < 0) {
+		fail("pipe write: %s\n", strerror(errno));
+		exit(KSFT_FAIL);
+	}
+
+	liov.iov_len = riov.iov_len = sizeof(buf);
+	liov.iov_base = buf;
+	riov.iov_base = mem;
+
+	if (process_vm_readv(getppid(), &liov, 1, &riov, 1, 0) < 0) {
+		if (errno == ENOSYS)
+			exit(KSFT_SKIP);
+		exit(KSFT_PASS);
+	}
+
+	exit(KSFT_FAIL);
+}
+
+static void try_ptrace(int fd, int pipefd[2])
+{
+	pid_t ppid = getppid();
+	int status;
+	char *mem;
+	long ret;
+
+	if (read(pipefd[0], &mem, sizeof(mem)) < 0) {
+		perror("pipe write");
+		exit(KSFT_FAIL);
+	}
+
+	ret = ptrace(PTRACE_ATTACH, ppid, 0, 0);
+	if (ret) {
+		perror("ptrace_attach");
+		exit(KSFT_FAIL);
+	}
+
+	ret = waitpid(ppid, &status, WUNTRACED);
+	if ((ret != ppid) || !(WIFSTOPPED(status))) {
+		fprintf(stderr, "weird waitppid result %ld stat %x\n",
+			ret, status);
+		exit(KSFT_FAIL);
+	}
+
+	if (ptrace(PTRACE_PEEKDATA, ppid, mem, 0))
+		exit(KSFT_PASS);
+
+	exit(KSFT_FAIL);
+}
+
+static void check_child_status(pid_t pid, const char *name)
+{
+	int status;
+
+	waitpid(pid, &status, 0);
+
+	if (WIFEXITED(status) && WEXITSTATUS(status) == KSFT_SKIP) {
+		skip("%s is not supported\n", name);
+		return;
+	}
+
+	if ((WIFEXITED(status) && WEXITSTATUS(status) == KSFT_PASS) ||
+	    WIFSIGNALED(status)) {
+		pass("%s is blocked as expected\n", name);
+		return;
+	}
+
+	fail("%s: unexpected memory access\n", name);
+}
+
+static void test_remote_access(int fd, const char *name,
+			       void (*func)(int fd, int pipefd[2]))
+{
+	int pipefd[2];
+	pid_t pid;
+	char *mem;
+
+	if (pipe(pipefd)) {
+		fail("pipe failed: %s\n", strerror(errno));
+		return;
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		fail("fork failed: %s\n", strerror(errno));
+		return;
+	}
+
+	if (pid == 0) {
+		func(fd, pipefd);
+		return;
+	}
+
+	mem = mmap(NULL, page_size, prot, mode, fd, 0);
+	if (mem == MAP_FAILED) {
+		fail("Unable to mmap secret memory\n");
+		return;
+	}
+
+	ftruncate(fd, page_size);
+	memset(mem, PATTERN, page_size);
+
+	if (write(pipefd[1], &mem, sizeof(mem)) < 0) {
+		fail("pipe write: %s\n", strerror(errno));
+		return;
+	}
+
+	check_child_status(pid, name);
+}
+
+static void test_process_vm_read(int fd)
+{
+	test_remote_access(fd, "process_vm_read", try_process_vm_read);
+}
+
+static void test_ptrace(int fd)
+{
+	test_remote_access(fd, "ptrace", try_ptrace);
+}
+
+static int set_cap_limits(rlim_t max)
+{
+	struct rlimit new;
+	cap_t cap = cap_init();
+
+	new.rlim_cur = max;
+	new.rlim_max = max;
+	if (setrlimit(RLIMIT_MEMLOCK, &new)) {
+		perror("setrlimit() returns error");
+		return -1;
+	}
+
+	/* drop capabilities including CAP_IPC_LOCK */
+	if (cap_set_proc(cap)) {
+		perror("cap_set_proc() returns error");
+		return -2;
+	}
+
+	return 0;
+}
+
+static void prepare(void)
+{
+	struct rlimit rlim;
+
+	page_size = sysconf(_SC_PAGE_SIZE);
+	if (!page_size)
+		ksft_exit_fail_msg("Failed to get page size %s\n",
+				   strerror(errno));
+
+	if (getrlimit(RLIMIT_MEMLOCK, &rlim))
+		ksft_exit_fail_msg("Unable to detect mlock limit: %s\n",
+				   strerror(errno));
+
+	mlock_limit_cur = rlim.rlim_cur;
+	mlock_limit_max = rlim.rlim_max;
+
+	printf("page_size: %ld, mlock.soft: %ld, mlock.hard: %ld\n",
+	       page_size, mlock_limit_cur, mlock_limit_max);
+
+	if (page_size > mlock_limit_cur)
+		mlock_limit_cur = page_size;
+	if (page_size > mlock_limit_max)
+		mlock_limit_max = page_size;
+
+	if (set_cap_limits(mlock_limit_max))
+		ksft_exit_fail_msg("Unable to set mlock limit: %s\n",
+				   strerror(errno));
+}
+
+#define NUM_TESTS 4
+
+int main(int argc, char *argv[])
+{
+	int fd;
+
+	prepare();
+
+	ksft_print_header();
+	ksft_set_plan(NUM_TESTS);
+
+	fd = memfd_secret(0);
+	if (fd < 0) {
+		if (errno == ENOSYS)
+			ksft_exit_skip("memfd_secret is not supported\n");
+		else
+			ksft_exit_fail_msg("memfd_secret failed: %s\n",
+					   strerror(errno));
+	}
+
+	test_mlock_limit(fd);
+	test_file_apis(fd);
+	test_process_vm_read(fd);
+	test_ptrace(fd);
+
+	close(fd);
+
+	ksft_exit(!ksft_get_fail_cnt());
+}
+
+#else /* __NR_memfd_secret */
+
+int main(int argc, char *argv[])
+{
+	printf("skip: skipping memfd_secret test (missing __NR_memfd_secret)\n");
+	return KSFT_SKIP;
+}
+
+#endif /* __NR_memfd_secret */
diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
index e953f3cd9664..95a67382f132 100755
--- a/tools/testing/selftests/vm/run_vmtests.sh
+++ b/tools/testing/selftests/vm/run_vmtests.sh
@@ -346,4 +346,21 @@ else
 	exitcode=1
 fi
 
+echo "running memfd_secret test"
+echo "------------------------------------"
+./memfd_secret
+ret_val=$?
+
+if [ $ret_val -eq 0 ]; then
+	echo "[PASS]"
+elif [ $ret_val -eq $ksft_skip ]; then
+	echo "[SKIP]"
+	exitcode=$ksft_skip
+else
+	echo "[FAIL]"
+	exitcode=1
+fi
+
+exit $exitcode
+
 exit $exitcode
-- 
2.28.0


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Re: [PATCH v20 4/7] mm: introduce memfd_secret system call to create "secret" memory areas

[Andrew Morton]

On Tue, 18 May 2021 10:20:31 +0300 Mike Rapoport <rppt@kernel.org> wrote:

> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> Introduce "memfd_secret" system call with the ability to create memory
> areas visible only in the context of the owning process and not mapped not
> only to other processes but in the kernel page tables as well.
> 
> ...
>
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -901,4 +901,9 @@ config KMAP_LOCAL
>  # struct io_mapping based helper.  Selected by drivers that need them
>  config IO_MAPPING
>  	bool
> +
> +config SECRETMEM
> +	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
> +	select STRICT_DEVMEM
> +
>  endmenu

WARNING: unmet direct dependencies detected for STRICT_DEVMEM
  Depends on [n]: MMU [=y] && DEVMEM [=n] && (ARCH_HAS_DEVMEM_IS_ALLOWED [=y] || GENERIC_LIB_DEVMEM_IS_ALLOWED [=n])
  Selected by [y]:
  - SECRETMEM [=y]

so I went back to the v19 version, with

--- a/mm/Kconfig~mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix
+++ a/mm/Kconfig
@@ -907,6 +907,5 @@ config IO_MAPPING
 
 config SECRETMEM
 	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
-	select STRICT_DEVMEM
 
 endmenu
_


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Re: [PATCH v20 4/7] mm: introduce memfd_secret system call to create "secret" memory areas

[Mike Rapoport]

On Tue, May 18, 2021 at 05:44:22PM -0700, Andrew Morton wrote:
> On Tue, 18 May 2021 10:20:31 +0300 Mike Rapoport <rppt@kernel.org> wrote:
> 
> > From: Mike Rapoport <rppt@linux.ibm.com>
> > 
> > Introduce "memfd_secret" system call with the ability to create memory
> > areas visible only in the context of the owning process and not mapped not
> > only to other processes but in the kernel page tables as well.
> > 
> > ...
> >
> > --- a/mm/Kconfig
> > +++ b/mm/Kconfig
> > @@ -901,4 +901,9 @@ config KMAP_LOCAL
> >  # struct io_mapping based helper.  Selected by drivers that need them
> >  config IO_MAPPING
> >  	bool
> > +
> > +config SECRETMEM
> > +	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
> > +	select STRICT_DEVMEM
> > +
> >  endmenu
> 
> WARNING: unmet direct dependencies detected for STRICT_DEVMEM
>   Depends on [n]: MMU [=y] && DEVMEM [=n] && (ARCH_HAS_DEVMEM_IS_ALLOWED [=y] || GENERIC_LIB_DEVMEM_IS_ALLOWED [=n])
>   Selected by [y]:
>   - SECRETMEM [=y]
> 
> so I went back to the v19 version, with

Ouch, sorry, I forgot to remove that hunk, v19 is the correct version.
 
> --- a/mm/Kconfig~mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix
> +++ a/mm/Kconfig
> @@ -907,6 +907,5 @@ config IO_MAPPING
>  
>  config SECRETMEM
>  	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
> -	select STRICT_DEVMEM
>  
>  endmenu
> _
> 

-- 
Sincerely yours,
Mike.

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