Avoid potential buffer overflow/missing zero termination of string (#…

…36408)

Co-authored-by: Elliot Saba <staticfloat@gmail.com>

src/dlload.c

@@ -190,7 +190,8 @@ JL_DLLEXPORT void *jl_load_dynamic_library(const char *modname, unsigned flags,
                     snprintf(relocated, PATHBUF, "%s%s", jl_options.julia_bindir, dl_path + 16);
                     len = len - 16 + strlen(jl_options.julia_bindir);
                 } else {
-                    strncpy(relocated, dl_path, len);
+                    strncpy(relocated, dl_path, PATHBUF);
+                    relocated[PATHBUF-1] = '\0';
                 }
                 for (i = 0; i < n_extensions; i++) {
                     const char *ext = extensions[i];

stdlib/Libdl/test/runtests.jl

@@ -222,4 +222,54 @@ let dl = C_NULL
     @test_skip !Libdl.dlclose(dl)   # Syscall doesn't fail on Win32
 end
 
+# test DL_LOAD_PATH handling and @executable_path expansion
+mktempdir() do dir
+    # Create a `libdcalltest` in a directory that is not on our load path
+    src_path = joinpath(private_libdir, "libccalltest.$(Libdl.dlext)")
+    dst_path = joinpath(dir, "libdcalltest.$(Libdl.dlext)")
+    cp(src_path, dst_path)
+
+    # Add an absurdly long entry to the load path to verify it doesn't lead to a buffer overflow
+    push!(Base.DL_LOAD_PATH, joinpath(dir, join(rand('a':'z', 10000))))
+
+    # Add the temporary directors to load path by absolute path
+    push!(Base.DL_LOAD_PATH, dir)
+
+    # Test that we can now open that file
+    Libdl.dlopen("libdcalltest") do dl
+        fptr = Libdl.dlsym(dl, :set_verbose)
+        @test fptr !== nothing
+        @test_throws ErrorException Libdl.dlsym(dl, :foo)
+
+        fptr = Libdl.dlsym_e(dl, :set_verbose)
+        @test fptr != C_NULL
+        fptr = Libdl.dlsym_e(dl, :foo)
+        @test fptr == C_NULL
+    end
+
+    # Skip these tests if the temporary directory is not on the same filesystem
+    # as the BINDIR, as in that case, a relative path will never work.
+    if Base.Filesystem.splitdrive(dir)[1] != Base.Filesystem.splitdrive(Sys.BINDIR)[1]
+        return
+    end
+
+    empty!(Base.DL_LOAD_PATH)
+    push!(Base.DL_LOAD_PATH, joinpath(dir, join(rand('a':'z', 10000))))
+
+    # Add this temporary directory to our load path, now using `@executable_path` to do so.
+    push!(Base.DL_LOAD_PATH, joinpath("@executable_path", relpath(dir, Sys.BINDIR)))
+
+    # Test that we can now open that file
+    Libdl.dlopen("libdcalltest") do dl
+        fptr = Libdl.dlsym(dl, :set_verbose)
+        @test fptr !== nothing
+        @test_throws ErrorException Libdl.dlsym(dl, :foo)
+
+        fptr = Libdl.dlsym_e(dl, :set_verbose)
+        @test fptr != C_NULL
+        fptr = Libdl.dlsym_e(dl, :foo)
+        @test fptr == C_NULL
+    end
+end
+
 end