The patch titled
Subject: selftest mm/mseal read-only elf memory segment
has been added to the -mm mm-unstable branch. Its filename is
selftest-mm-mseal-read-only-elf-memory-segment.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftest-mm-mseal-read-only-elf-memory-segment.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jeff Xu <jeffxu@xxxxxxxxxxxx>
Subject: selftest mm/mseal read-only elf memory segment
Date: Mon, 15 Apr 2024 16:35:24 +0000
Sealing read-only of elf mapping so it can't be changed by mprotect.
Link: https://lkml.kernel.org/r/20240415163527.626541-6-jeffxu@xxxxxxxxxxxx
Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jeff Xu <jeffxu@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Jorge Lucangeli Obes <jorgelo@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Cc: Pedro Falcato <pedro.falcato@xxxxxxxxx>
Cc: Stephen Röttger <sroettger@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/mm/.gitignore | 1
tools/testing/selftests/mm/Makefile | 1
tools/testing/selftests/mm/seal_elf.c | 183 ++++++++++++++++++++++++
3 files changed, 185 insertions(+)
--- a/tools/testing/selftests/mm/.gitignore~selftest-mm-mseal-read-only-elf-memory-segment
+++ a/tools/testing/selftests/mm/.gitignore
@@ -48,3 +48,4 @@ va_high_addr_switch
hugetlb_fault_after_madv
hugetlb_madv_vs_map
mseal_test
+seal_elf
--- a/tools/testing/selftests/mm/Makefile~selftest-mm-mseal-read-only-elf-memory-segment
+++ a/tools/testing/selftests/mm/Makefile
@@ -60,6 +60,7 @@ TEST_GEN_FILES += mrelease_test
TEST_GEN_FILES += mremap_dontunmap
TEST_GEN_FILES += mremap_test
TEST_GEN_FILES += mseal_test
+TEST_GEN_FILES += seal_elf
TEST_GEN_FILES += on-fault-limit
TEST_GEN_FILES += pagemap_ioctl
TEST_GEN_FILES += thuge-gen
--- /dev/null
+++ a/tools/testing/selftests/mm/seal_elf.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <sys/mman.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <stdbool.h>
+#include "../kselftest.h"
+#include <syscall.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <sys/ioctl.h>
+#include <sys/vfs.h>
+#include <sys/stat.h>
+
+/*
+ * need those definition for manually build using gcc.
+ * gcc -I ../../../../usr/include -DDEBUG -O3 -DDEBUG -O3 seal_elf.c -o seal_elf
+ */
+#define FAIL_TEST_IF_FALSE(c) do {\
+ if (!(c)) {\
+ ksft_test_result_fail("%s, line:%d\n", __func__, __LINE__);\
+ goto test_end;\
+ } \
+ } \
+ while (0)
+
+#define SKIP_TEST_IF_FALSE(c) do {\
+ if (!(c)) {\
+ ksft_test_result_skip("%s, line:%d\n", __func__, __LINE__);\
+ goto test_end;\
+ } \
+ } \
+ while (0)
+
+
+#define TEST_END_CHECK() {\
+ ksft_test_result_pass("%s\n", __func__);\
+ return;\
+test_end:\
+ return;\
+}
+
+#ifndef u64
+#define u64 unsigned long long
+#endif
+
+/*
+ * define sys_xyx to call syscall directly.
+ */
+static int sys_mseal(void *start, size_t len)
+{
+ int sret;
+
+ errno = 0;
+ sret = syscall(__NR_mseal, start, len, 0);
+ return sret;
+}
+
+static void *sys_mmap(void *addr, unsigned long len, unsigned long prot,
+ unsigned long flags, unsigned long fd, unsigned long offset)
+{
+ void *sret;
+
+ errno = 0;
+ sret = (void *) syscall(__NR_mmap, addr, len, prot,
+ flags, fd, offset);
+ return sret;
+}
+
+inline int sys_mprotect(void *ptr, size_t size, unsigned long prot)
+{
+ int sret;
+
+ errno = 0;
+ sret = syscall(__NR_mprotect, ptr, size, prot);
+ return sret;
+}
+
+static bool seal_support(void)
+{
+ int ret;
+ void *ptr;
+ unsigned long page_size = getpagesize();
+
+ ptr = sys_mmap(NULL, page_size, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+ if (ptr == (void *) -1)
+ return false;
+
+ ret = sys_mseal(ptr, page_size);
+ if (ret < 0)
+ return false;
+
+ return true;
+}
+
+const char somestr[4096] = {"READONLY"};
+
+static void test_seal_elf(void)
+{
+ int ret;
+ FILE *maps;
+ char line[512];
+ int size = 0;
+ uintptr_t addr_start, addr_end;
+ char prot[5];
+ char filename[256];
+ unsigned long page_size = getpagesize();
+ unsigned long long ptr = (unsigned long long) somestr;
+ char *somestr2 = (char *)somestr;
+
+ /*
+ * Modify the protection of readonly somestr
+ */
+ if (((unsigned long long)ptr % page_size) != 0)
+ ptr = (unsigned long long)ptr & ~(page_size - 1);
+
+ ksft_print_msg("somestr = %s\n", somestr);
+ ksft_print_msg("change protection to rw\n");
+ ret = sys_mprotect((void *)ptr, page_size, PROT_READ|PROT_WRITE);
+ FAIL_TEST_IF_FALSE(!ret);
+ *somestr2 = 'A';
+ ksft_print_msg("somestr is modified to: %s\n", somestr);
+ ret = sys_mprotect((void *)ptr, page_size, PROT_READ);
+ FAIL_TEST_IF_FALSE(!ret);
+
+ maps = fopen("/proc/self/maps", "r");
+ FAIL_TEST_IF_FALSE(maps);
+
+ /*
+ * apply sealing to elf binary
+ */
+ while (fgets(line, sizeof(line), maps)) {
+ if (sscanf(line, "%lx-%lx %4s %*x %*x:%*x %*u %255[^\n]",
+ &addr_start, &addr_end, &prot, &filename) == 4) {
+ if (strlen(filename)) {
+ /*
+ * seal the mapping if read only.
+ */
+ if (strstr(prot, "r-")) {
+ ret = sys_mseal((void *)addr_start, addr_end - addr_start);
+ FAIL_TEST_IF_FALSE(!ret);
+ ksft_print_msg("sealed: %lx-%lx %s %s\n",
+ addr_start, addr_end, prot, filename);
+ if ((uintptr_t) somestr >= addr_start &&
+ (uintptr_t) somestr <= addr_end)
+ ksft_print_msg("mapping for somestr found\n");
+ }
+ }
+ }
+ }
+ fclose(maps);
+
+ ret = sys_mprotect((void *)ptr, page_size, PROT_READ | PROT_WRITE);
+ FAIL_TEST_IF_FALSE(ret < 0);
+ ksft_print_msg("somestr is sealed, mprotect is rejected\n");
+
+ TEST_END_CHECK();
+}
+
+int main(int argc, char **argv)
+{
+ bool test_seal = seal_support();
+
+ ksft_print_header();
+ ksft_print_msg("pid=%d\n", getpid());
+
+ if (!test_seal)
+ ksft_exit_skip("sealing not supported, check CONFIG_64BIT\n");
+
+ ksft_set_plan(1);
+
+ test_seal_elf();
+
+ ksft_finished();
+ return 0;
+}
_
Patches currently in -mm which might be from jeffxu@xxxxxxxxxxxx are
mseal-wire-up-mseal-syscall.patch
mseal-add-mseal-syscall.patch
selftest-mm-mseal-memory-sealing.patch
mseal-add-documentation.patch
selftest-mm-mseal-read-only-elf-memory-segment.patch
