Merge "libfstab_fuzzer: fuzz TransformFstabForDsu() and skip mount logic"

fs_mgr/fs_mgr_fstab.cpp

@@ -754,10 +754,11 @@ bool ReadFstabFromDt(Fstab* fstab, bool verbose) {
 }
 
 #ifdef NO_SKIP_MOUNT
-bool SkipMountingPartitions(Fstab*, bool) {
-    return true;
-}
+static constexpr bool kNoSkipMount = true;
 #else
+static constexpr bool kNoSkipMount = false;
+#endif
+
 // For GSI to skip mounting /product and /system_ext, until there are well-defined interfaces
 // between them and /system. Otherwise, the GSI flashed on /system might not be able to work with
 // device-specific /product and /system_ext. skip_mount.cfg belongs to system_ext partition because
@@ -765,17 +766,24 @@ bool SkipMountingPartitions(Fstab*, bool) {
 // /system/system_ext because GSI is a single system.img that includes the contents of system_ext
 // partition and product partition under /system/system_ext and /system/product, respectively.
 bool SkipMountingPartitions(Fstab* fstab, bool verbose) {
-    static constexpr char kSkipMountConfig[] = "/system/system_ext/etc/init/config/skip_mount.cfg";
-
-    std::string skip_config;
-    auto save_errno = errno;
-    if (!ReadFileToString(kSkipMountConfig, &skip_config)) {
-        errno = save_errno;  // missing file is expected
+    if (kNoSkipMount) {
         return true;
     }
 
+    static constexpr char kSkipMountConfig[] = "/system/system_ext/etc/init/config/skip_mount.cfg";
+
+    std::string skip_mount_config;
+    auto save_errno = errno;
+    if (!ReadFileToString(kSkipMountConfig, &skip_mount_config)) {
+        errno = save_errno;  // missing file is expected
+        return true;
+    }
+    return SkipMountWithConfig(skip_mount_config, fstab, verbose);
+}
+
+bool SkipMountWithConfig(const std::string& skip_mount_config, Fstab* fstab, bool verbose) {
     std::vector<std::string> skip_mount_patterns;
-    for (const auto& line : Split(skip_config, "\n")) {
+    for (const auto& line : Split(skip_mount_config, "\n")) {
         if (line.empty() || StartsWith(line, "#")) {
             continue;
         }
@@ -801,7 +809,6 @@ bool SkipMountingPartitions(Fstab* fstab, bool verbose) {
     fstab->erase(remove_from, fstab->end());
     return true;
 }
-#endif
 
 // Loads the fstab file and combines with fstab entries passed in from device tree.
 bool ReadDefaultFstab(Fstab* fstab) {

fs_mgr/fuzz/fs_mgr_fstab_fuzzer.cpp

@@ -14,13 +14,27 @@
 // limitations under the License.
 //
 
-#include <cstdio>
+#include <string>
+#include <vector>
 
 #include <fstab/fstab.h>
+#include <fuzzer/FuzzedDataProvider.h>
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
-    std::string make_fstab_str(reinterpret_cast<const char*>(data), size);
+    FuzzedDataProvider fdp(data, size);
+
+    std::string make_fstab_str = fdp.ConsumeRandomLengthString();
+    std::string dsu_slot = fdp.ConsumeRandomLengthString(30);
+    std::vector<std::string> dsu_partitions = {
+            fdp.ConsumeRandomLengthString(30),
+            fdp.ConsumeRandomLengthString(30),
+    };
+    std::string skip_mount_config = fdp.ConsumeRemainingBytesAsString();
+
     android::fs_mgr::Fstab fstab;
     android::fs_mgr::ParseFstabFromString(make_fstab_str, /* proc_mounts = */ false, &fstab);
+    android::fs_mgr::TransformFstabForDsu(&fstab, dsu_slot, dsu_partitions);
+    android::fs_mgr::SkipMountWithConfig(skip_mount_config, &fstab, /* verbose = */ false);
+
     return 0;
 }

fs_mgr/include_fstab/fstab/fstab.h

@@ -97,6 +97,8 @@ using Fstab = std::vector<FstabEntry>;
 bool ParseFstabFromString(const std::string& fstab_str, bool proc_mounts, Fstab* fstab_out);
 // Exported for testability. Regular users should use ReadDefaultFstab().
 std::string GetFstabPath();
+// Exported for testability.
+bool SkipMountWithConfig(const std::string& skip_config, Fstab* fstab, bool verbose);
 
 bool ReadFstabFromFile(const std::string& path, Fstab* fstab);
 bool ReadFstabFromDt(Fstab* fstab, bool verbose = true);