Change pointer in Bypass variant to PathBuf to fix dangling pointer bug

mirrord/layer/src/common.rs

@@ -110,12 +110,7 @@ impl CheckedInto<PathBuf> for *const c_char {
                 // `stripped_path` is a reference to a later character in the same string as
                 // `path_str`, `stripped_path.as_ptr()` returns a pointer to a later index
                 // in the same string owned by the caller (the hooked program).
-                Detour::Bypass(Bypass::FileOperationInMirrordBinTempDir(
-                    // TODO: dangling pointer bug - old code relied on fact that string was owned
-                    // elsewhere now the result of to_string_lossy is
-                    // short-lived
-                    stripped_path.as_os_str().as_encoded_bytes().as_ptr() as _,
-                ))
+                Detour::Bypass(Bypass::FileOperationInMirrordBinTempDir(stripped_path))
             } else {
                 Detour::Success(path_str) // strip is None, path not in temp dir.
             }

mirrord/layer/src/detour.rs

@@ -11,9 +11,6 @@ use core::{
 };
 use std::{cell::RefCell, ops::Deref, os::unix::prelude::*, path::PathBuf, sync::OnceLock};
 
-#[cfg(target_os = "macos")]
-use libc::c_char;
-
 use crate::error::HookError;
 
 thread_local!(
@@ -147,7 +144,7 @@ pub(crate) enum Bypass {
     /// We hooked a file operation on a path in mirrord's bin directory. So do the operation
     /// locally, but on the original path, not the one in mirrord's dir.
     #[cfg(target_os = "macos")]
-    FileOperationInMirrordBinTempDir(*const c_char),
+    FileOperationInMirrordBinTempDir(PathBuf),
 
     /// File [`PathBuf`] should be ignored (used for tests).
     IgnoredFile(PathBuf),

mirrord/layer/src/exec_utils.rs

@@ -282,7 +282,8 @@ pub(crate) unsafe extern "C" fn _nsget_executable_path_detour(
     let res = FN__NSGET_EXECUTABLE_PATH(path, buflen);
     if res == 0 {
         let path_buf_detour = CheckedInto::<PathBuf>::checked_into(path as *const c_char);
-        if let Bypass(FileOperationInMirrordBinTempDir(later_ptr)) = path_buf_detour {
+        if let Bypass(FileOperationInMirrordBinTempDir(path_buf)) = path_buf_detour {
+            let later_ptr: *const i8 = path_buf.as_os_str().as_encoded_bytes().as_ptr() as _;
             // SAFETY: If we're here, the original function was passed this pointer and was
             //         successful, so this pointer must be valid.
             let old_len = *buflen;
@@ -325,9 +326,9 @@ pub(crate) unsafe extern "C" fn dlopen_detour(
     // we hold the guard manually for tracing/internal code
     let guard = crate::detour::DetourGuard::new();
     let detour: Detour<PathBuf> = raw_path.checked_into();
-    let raw_path = if let Bypass(FileOperationInMirrordBinTempDir(ptr)) = detour {
+    let raw_path = if let Bypass(FileOperationInMirrordBinTempDir(path_buf)) = detour {
         trace!("dlopen called with a path inside our patch dir, switching with fixed pointer.");
-        ptr
+        path_buf.as_os_str().as_encoded_bytes().as_ptr() as _
     } else {
         trace!("dlopen called on path {detour:?}.");
         raw_path

mirrord/layer/src/file/hooks.rs

@@ -57,7 +57,9 @@ fn update_ptr_from_bypass(ptr: *const c_char, bypass: Bypass) -> *const c_char {
         // inside mirrord's temp bin dir. The detour has returned us the original path of the file
         // (stripped mirrord's dir path), so now we carry out the operation locally, on the stripped
         // path.
-        Bypass::FileOperationInMirrordBinTempDir(stripped_ptr) => stripped_ptr,
+        Bypass::FileOperationInMirrordBinTempDir(path_buf) => {
+            path_buf.as_os_str().as_encoded_bytes().as_ptr() as _
+        }
         _ => ptr,
     }
 }