nixpkgs/pkgs/applications/virtualization/qemu/force-uid0-on-9p.patch

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 3f271fc..dc273f4 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -45,6 +45,23 @@
 
 #define VIRTFS_META_DIR ".virtfs_metadata"
 
+static int is_in_store_path(const char *path)
+{
+    static char *store_path = NULL;
+    int store_path_len = -1;
+
+    if (store_path_len == -1) {
+        if ((store_path = getenv("NIX_STORE")) != NULL)
+            store_path_len = strlen(store_path);
+        else
+            store_path_len = 0;
+    }
+
+    if (store_path_len > 0)
+        return strncmp(path, store_path, strlen(store_path)) == 0;
+    return 0;
+}
+
 static char *local_mapped_attr_path(FsContext *ctx, const char *path)
 {
     int dirlen;
@@ -128,6 +145,8 @@ static int local_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
     if (err) {
         goto err_out;
     }
+    stbuf->st_uid = 0;
+    stbuf->st_gid = 0;
     if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
         /* Actual credentials are part of extended attrs */
         uid_t tmp_uid;
@@ -462,6 +481,11 @@ static ssize_t local_pwritev(FsContext *ctx, V9fsFidOpenState *fs,
     return ret;
 }
 
+static inline int maybe_chmod(const char *path, mode_t mode)
+{
+    return is_in_store_path(path) ? 0 : chmod(path, mode);
+}
+
 static int local_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
 {
     char *buffer;
@@ -477,7 +501,7 @@ static int local_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
     } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
                (fs_ctx->export_flags & V9FS_SM_NONE)) {
         buffer = rpath(fs_ctx, path);
-        ret = chmod(buffer, credp->fc_mode);
+        ret = maybe_chmod(buffer, credp->fc_mode);
         g_free(buffer);
     }
     return ret;
@@ -621,6 +645,8 @@ static int local_fstat(FsContext *fs_ctx, int fid_type,
     if (err) {
         return err;
     }
+    stbuf->st_uid = 0;
+    stbuf->st_gid = 0;
     if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
         /* Actual credentials are part of extended attrs */
         uid_t tmp_uid;
@@ -916,7 +942,8 @@ static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
         (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
         (fs_ctx->export_flags & V9FS_SM_NONE)) {
         buffer = rpath(fs_ctx, path);
-        ret = lchown(buffer, credp->fc_uid, credp->fc_gid);
+        ret = is_in_store_path(buffer)
+            ? 0 : lchown(buffer, credp->fc_uid, credp->fc_gid);
         g_free(buffer);
     } else if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
         buffer = rpath(fs_ctx, path);