[Qemu-devel] [V4 PATCH 5/8] Create support in chroot environment

["M. Mohan Kumar" <mohan@in.ibm.com>]

Add both server & client side interfaces to create regular files in
chroot environment

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
---
 hw/9pfs/virtio-9p-chroot.c |   41 +++++++++++++++++++++++++++++++++++++++++
 hw/9pfs/virtio-9p-local.c  |   22 ++++++++++++++++++++--
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/hw/9pfs/virtio-9p-chroot.c b/hw/9pfs/virtio-9p-chroot.c
index 7da0702..890dd78 100644
--- a/hw/9pfs/virtio-9p-chroot.c
+++ b/hw/9pfs/virtio-9p-chroot.c
@@ -227,6 +227,44 @@ static void chroot_do_open(V9fsFileObjectRequest *request, FdInfo *fd_info)
     }
 }
 
+/*
+ * Helper routine to create a file and return the file descriptor and
+ * error status in FdInfo structure.
+ */
+static void chroot_do_create(V9fsFileObjectRequest *request, FdInfo *fd_info)
+{
+    uid_t cur_uid;
+    gid_t cur_gid;
+
+    cur_uid = geteuid();
+    cur_gid = getegid();
+
+    fd_info->fi_fd = -1;
+
+    if (setfsuid(request->data.uid) < 0) {
+        fd_info->fi_error = errno;
+        return;
+    }
+    if (setfsgid(request->data.gid) < 0) {
+        fd_info->fi_error = errno;
+        goto unset_uid;
+    }
+
+    fd_info->fi_fd = open(request->path.path, request->data.flags,
+                        request->data.mode);
+
+    if (fd_info->fi_fd < 0) {
+        fd_info->fi_error = errno;
+    } else {
+        fd_info->fi_error = 0;
+        fd_info->fi_flags = FI_FDVALID;
+    }
+
+    setfsgid(cur_gid);
+unset_uid:
+    setfsuid(cur_uid);
+}
+
 static int chroot_daemonize(int chroot_sock)
 {
     sigset_t sigset;
@@ -324,6 +362,9 @@ int v9fs_chroot(FsContext *fs_ctx)
         case T_OPEN:
             chroot_do_open(&request, &fd_info);
             break;
+        case T_CREATE:
+            chroot_do_create(&request, &fd_info);
+            break;
         default:
             fd_info.fi_fd = 0;
             fd_info.fi_error = EIO;
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index 96e8181..afb088a 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -52,6 +52,23 @@ static int passthrough_open(FsContext *fs_ctx, const char *path, int flags)
     return fd;
 }
 
+static int passthrough_create(FsContext *fs_ctx, const char *path, int flags,
+                    FsCred *credp)
+{
+    V9fsFileObjectRequest request;
+    int fd, error = 0;
+
+    fill_request(&request, path, credp);
+    request.data.flags = flags;
+    request.data.type = T_CREATE;
+    fd = v9fs_request(fs_ctx, &request, &error);
+    if (fd < 0) {
+        errno = error;
+    }
+    qemu_free((void *)request.path.path);
+    return fd;
+}
+
 static int local_lstat(FsContext *fs_ctx, const char *path, struct stat *stbuf)
 {
     int err;
@@ -376,8 +393,7 @@ static int local_open2(FsContext *fs_ctx, const char *path, int flags,
             serrno = errno;
             goto err_end;
         }
-    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
-               (fs_ctx->fs_sm == SM_NONE)) {
+    } else if (fs_ctx->fs_sm == SM_NONE) {
         fd = open(rpath(fs_ctx, path), flags, credp->fc_mode);
         if (fd == -1) {
             return fd;
@@ -387,6 +403,8 @@ static int local_open2(FsContext *fs_ctx, const char *path, int flags,
             serrno = errno;
             goto err_end;
         }
+    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        fd = passthrough_create(fs_ctx, path, flags, credp);
     }
     return fd;
 
-- 
1.7.3.4