From 4e1776cedfaa68fab341e657e025ae31eb95f194 Mon Sep 17 00:00:00 2001
From: Will Deacon <willdeacon@google.com>
Date: Fri, 31 May 2024 15:34:18 +0000
Subject: [PATCH 1/2] Revert "Load modules from _16K dir when running on 16K
 kernel"

This reverts commit ffdb017e7d0141d09d67c735913196a8dc166671.

Overriding an explicitly-specified module path (e.g. passed via the
'-d <path>' argument) because the kernel is using 16KiB pages is
inconsistent and unexpected. Revert this change in anticipation of
filtering incompatible modules instead.

Bug: 343971855
Test: Verified that _16k module directory is excluded by modprobe when running in userspace fastboot with 4k pages.
Change-Id: If9c6e2d26fc53b12f543d531d64ef3d288ddc179
---
 toolbox/modprobe.cpp | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/toolbox/modprobe.cpp b/toolbox/modprobe.cpp
index b0e76ea81..45dd9b8c1 100644
--- a/toolbox/modprobe.cpp
+++ b/toolbox/modprobe.cpp
@@ -15,7 +15,6 @@
  */
 
 #include <ctype.h>
-#include <fcntl.h>
 #include <getopt.h>
 #include <stdlib.h>
 
@@ -28,7 +27,6 @@
 #include <modprobe/modprobe.h>
 
 #include <sys/utsname.h>
-#include <unistd.h>
 
 namespace {
 
@@ -107,11 +105,6 @@ static int KernelVersionNameFilter(const dirent* de) {
     return 0;
 }
 
-std::string GetPageSizeSuffix() {
-    static const size_t page_size = sysconf(_SC_PAGE_SIZE);
-    return android::base::StringPrintf("_%zuk", page_size / 1024);
-}
-
 }  // anonymous namespace
 
 extern "C" int modprobe_main(int argc, char** argv) {
@@ -240,19 +233,6 @@ extern "C" int modprobe_main(int argc, char** argv) {
         // Allow modules to be directly inside /lib/modules
         mod_dirs.emplace_back(LIB_MODULES_PREFIX);
     }
-    if (getpagesize() != 4096) {
-        struct utsname uts {};
-        if (uname(&uts)) {
-            PLOG(FATAL) << "Failed to get kernel version";
-        }
-        const auto module_dir = android::base::StringPrintf("/lib/modules/%s%s", uts.release,
-                                                            GetPageSizeSuffix().c_str());
-        struct stat st {};
-        if (stat(module_dir.c_str(), &st) == 0 && S_ISDIR(st.st_mode)) {
-            mod_dirs.clear();
-            mod_dirs.emplace_back(module_dir);
-        }
-    }
 
     LOG(DEBUG) << "mode is " << mode;
     LOG(DEBUG) << "mod_dirs is: " << android::base::Join(mod_dirs, " ");

From c991c3dbedd35d5291c68da15681b8b1efd02f9c Mon Sep 17 00:00:00 2001
From: Will Deacon <willdeacon@google.com>
Date: Fri, 31 May 2024 17:25:49 +0000
Subject: [PATCH 2/2] toolbox/modprobe: Filter module directories based on
 kernel page size

When modules for multiple kernels with the same major/minor versions
are installed on a device, modprobe will search the module directories
based on whatever order scandir() returned them. In this case, it is
possible that we will try to load modules with the wrong page size for
the running kernel, which can lead to obscure symbol CRC mismatches and
ultimately a system crash.

Adjust the scandir() filtering function so that the kernel page size is
taken into account in addition to the major/minor versions returned by
utsname(). The general rule is that module directories ending in "_Nk"
contain modules for a page-size of N KiB, whilst the absence of such
a suffix implies the default of 4 KiB.

Bug: 343971855
Test: Verified that _16k module directory is excluded by modprobe when running in userspace fastboot with 4k pages.
Change-Id: I78a0a249028bbb0bcdd78eb14de36e631e233be0
---
 toolbox/modprobe.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/toolbox/modprobe.cpp b/toolbox/modprobe.cpp
index 45dd9b8c1..7fde4915e 100644
--- a/toolbox/modprobe.cpp
+++ b/toolbox/modprobe.cpp
@@ -17,6 +17,7 @@
 #include <ctype.h>
 #include <getopt.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include <string>
 
@@ -85,6 +86,20 @@ void MyLogger(android::base::LogId id, android::base::LogSeverity severity, cons
     }
 }
 
+static bool ModDirMatchesKernelPageSize(const char* mod_dir) {
+    static const unsigned int kernel_pgsize_kb = getpagesize() / 1024;
+    const char* mod_sfx = strrchr(mod_dir, '_');
+    unsigned int mod_pgsize_kb;
+    int mod_sfx_len;
+
+    if (mod_sfx == NULL || sscanf(mod_sfx, "_%uk%n", &mod_pgsize_kb, &mod_sfx_len) != 1 ||
+        strlen(mod_sfx) != mod_sfx_len) {
+        mod_pgsize_kb = 4;
+    }
+
+    return kernel_pgsize_kb == mod_pgsize_kb;
+}
+
 // Find directories in format of "/lib/modules/x.y.z-*".
 static int KernelVersionNameFilter(const dirent* de) {
     unsigned int major, minor;
@@ -100,7 +115,7 @@ static int KernelVersionNameFilter(const dirent* de) {
     }
 
     if (android::base::StartsWith(de->d_name, kernel_version)) {
-        return 1;
+        return ModDirMatchesKernelPageSize(de->d_name);
     }
     return 0;
 }