[WASMFS] Enforce file name char limit (#15641)

Relevant Issue: #15041
- Enforce file name character limit

system/lib/wasmfs/syscalls.cpp

@@ -27,6 +27,9 @@
 // Used to improve readability compared to those in stat.h
 #define WASMFS_PERM_WRITE 0222
 
+// In Linux, the maximum length for a filename is 255 bytes.
+#define WASMFS_NAME_MAX 255
+
 extern "C" {
 
 using namespace wasmfs;
@@ -440,6 +443,9 @@ static __wasi_fd_t doOpen(char* pathname,
   }
 
   auto base = pathParts.back();
+  if (base.size() > WASMFS_NAME_MAX) {
+    return -ENAMETOOLONG;
+  }
 
   // Root directory
   if (pathParts.size() == 1 && pathParts[0] == "/") {
@@ -534,6 +540,9 @@ static long doMkdir(char* path, long mode, backend_t backend = NullBackend) {
   }
 
   auto base = pathParts.back();
+  if (base.size() > WASMFS_NAME_MAX) {
+    return -ENAMETOOLONG;
+  }
 
   long err;
   auto parentDir = getDir(pathParts.begin(), pathParts.end() - 1, err);
@@ -831,7 +840,6 @@ long __syscall_getdents64(long fd, long dirp, long count) {
     result->d_reclen = sizeof(dirent);
     result->d_type =
       curr.file->is<Directory>() ? DT_DIR : DT_REG; // TODO: add symlinks.
-    // TODO: Enforce that the name can fit in the d_name field.
     assert(curr.name.size() + 1 <= sizeof(result->d_name));
     strcpy(result->d_name, curr.name.c_str());
     ++result;
@@ -916,6 +924,9 @@ long __syscall_rename(long old_path, long new_path) {
   }
 
   auto newBase = newPathParts.back();
+  if (newBase.size() > WASMFS_NAME_MAX) {
+    return -ENAMETOOLONG;
+  }
 
   // oldPath is the forbidden ancestor.
   auto newParentDir =

tests/stdio/test_rename.c

@@ -116,6 +116,18 @@ void test() {
   assert(err == -1);
   assert(errno == EACCES);
 
+  // Can't rename a file with a new path name that is longer than WASMFS_NAME_MAX.
+#ifdef WASMFS
+  errno = 0;
+  rename("dir",
+         "000000000100000000020000000003000000000400000000050000000006000000000"
+         "700000000080000000009000000000000000000010000000002000000000300000000"
+         "040000000005000000000600000000070000000008000000000900000000000000000"
+         "0010000000002000000000300000000040000000005123456");
+
+  assert(errno == ENAMETOOLONG);
+#endif
+  
   // Can't use an empty path for oldpath.
   err = rename("", "test");
   assert(err == -1);
@@ -133,7 +145,8 @@ void test() {
   
   err = rename("dir", "dir/somename/noexist");
   assert(err == -1);
-  // In the JS file system, this returns ENOENT rather than detecting that dir is an ancestor.
+  // In the JS file system, this returns ENOENT rather than detecting that dir
+  // is an ancestor.
 #ifdef WASMFS
   assert(errno == EINVAL);
 #else

tests/wasmfs/wasmfs_create.c

@@ -87,6 +87,17 @@ int main() {
   printf("File contents: %s", buf3);
   assert(errno == 0);
 
+  // Try to make a file with a name that is greater than WASMFS_NAME_MAX.
+  errno = 0;
+  open("00000000010000000002000000000300000000040000000005000000000600000000070"
+       "00000000800000000090000000000000000000100000000020000000003000000000400"
+       "00000005000000000600000000070000000008000000000900000000000000000001000"
+       "0000002000000000300000000040000000005123456",
+       O_RDWR);
+#ifdef WASMFS
+  assert(errno == ENAMETOOLONG);
+#endif
+
   // TODO: use seek to test out of bounds read.
 
   return 0;

tests/wasmfs/wasmfs_mkdir.c

@@ -105,5 +105,19 @@ int main() {
   printf("Errno: %s\n", strerror(errno));
   assert(errno == 0);
 
+  // Try to make a directory with a name that is longer than WASMFS_NAME_MAX.
+  // In Linux, creating a directory with a name that is longer than 255
+  // characters returns ENAMETOOLONG.
+  errno = 0;
+  mkdir("/working/"
+        "0000000001000000000200000000030000000004000000000500000000060000000007"
+        "0000000008000000000900000000000000000001000000000200000000030000000004"
+        "0000000005000000000600000000070000000008000000000900000000000000000001"
+        "0000000002000000000300000000040000000005123456",
+        0777);
+#ifdef WASMFS
+  assert(errno == ENAMETOOLONG);
+#endif
+
   return 0;
 }