[Qemu-devel] [V4 PATCH 4/8] Add support to open a file in chroot environment

[M. Mohan Kumar]

This patch adds both server and client side support to open a file
(directory) in the chroot environment

Signed-off-by: M. Mohan Kumar <address@hidden>
---
 hw/9pfs/virtio-9p-chroot.c |   53 ++++++++++++++++++++++++++++++++++++++-----
 hw/9pfs/virtio-9p-chroot.h |    1 +
 hw/9pfs/virtio-9p-local.c  |   52 +++++++++++++++++++++++++++++++++++++++---
 3 files changed, 95 insertions(+), 11 deletions(-)

diff --git a/hw/9pfs/virtio-9p-chroot.c b/hw/9pfs/virtio-9p-chroot.c
index b466d9a..7da0702 100644
--- a/hw/9pfs/virtio-9p-chroot.c
+++ b/hw/9pfs/virtio-9p-chroot.c
@@ -191,6 +191,42 @@ static int v9fs_write_request(int sockfd, 
V9fsFileObjectRequest *request)
     return 0;
 }
 
+/* Return opened file descriptor on success or -1 on error */
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *request,
+                        int *error)
+{
+    int fd;
+    pthread_mutex_lock(&fs_ctx->chroot_mutex);
+    if (fs_ctx->chroot_ioerror) {
+        *error = EIO;
+        fd = -1;
+        goto unlock;
+    }
+    v9fs_write_request(fs_ctx->chroot_socket, request);
+    fd = v9fs_receivefd(fs_ctx->chroot_socket, error);
+    if (fd == -EIO) {
+        fs_ctx->chroot_ioerror = 1;
+    }
+unlock:
+    pthread_mutex_unlock(&fs_ctx->chroot_mutex);
+    return fd;
+}
+
+/*
+ * Helper routine to open a file and return fd and error status in
+ * FdInfo structure
+ */
+static void chroot_do_open(V9fsFileObjectRequest *request, FdInfo *fd_info)
+{
+    fd_info->fi_fd = open(request->path.path, request->data.flags);
+    if (fd_info->fi_fd < 0) {
+        fd_info->fi_error = errno;
+    } else {
+        fd_info->fi_error = 0;
+        fd_info->fi_flags = FI_FDVALID;
+    }
+}
+
 static int chroot_daemonize(int chroot_sock)
 {
     sigset_t sigset;
@@ -219,12 +255,6 @@ static int chroot_daemonize(int chroot_sock)
     return 0;
 }
 
-static void chroot_dummy(void)
-{
-    (void)v9fs_receivefd;
-    (void)v9fs_write_request;
-}
-
 /*
  * Fork a process and chroot into the share path. Communication
  * between qemu process and chroot process happens via socket
@@ -270,7 +300,6 @@ int v9fs_chroot(FsContext *fs_ctx)
         error = qemu_write_full(chroot_sock, &code, sizeof(code));
         _exit(1);
     }
-    chroot_dummy();
 
     /*
      * Write 0 to chroot socket to indicate chroot process creation is
@@ -291,6 +320,16 @@ int v9fs_chroot(FsContext *fs_ctx)
             chroot_sendfd(chroot_sock, &fd_info);
             continue;
         }
+        switch (request.data.type) {
+        case T_OPEN:
+            chroot_do_open(&request, &fd_info);
+            break;
+        default:
+            fd_info.fi_fd = 0;
+            fd_info.fi_error = EIO;
+            break;
+        }
+        chroot_sendfd(chroot_sock, &fd_info);
         qemu_free((void *)request.path.path);
         if (request.data.oldpath_len) {
             qemu_free((void *)request.path.old_path);
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
index 6f3fd14..ffeeddc 100644
--- a/hw/9pfs/virtio-9p-chroot.h
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -37,5 +37,6 @@ typedef struct V9fsFileObjectRequest
 
 
 int v9fs_chroot(FsContext *fs_ctx);
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *or, int *error);
 
 #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index 0a015de..96e8181 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -13,6 +13,7 @@
 #include "virtio.h"
 #include "virtio-9p.h"
 #include "virtio-9p-xattr.h"
+#include "virtio-9p-chroot.h"
 #include <arpa/inet.h>
 #include <pwd.h>
 #include <grp.h>
@@ -20,6 +21,36 @@
 #include <sys/un.h>
 #include <attr/xattr.h>
 
+/* Helper routine to fill V9fsFileObjectRequest structure */
+static void fill_request(V9fsFileObjectRequest *request, const char *path,
+                FsCred *credp)
+{
+    memset(request, 0, sizeof(*request));
+    request->data.path_len = strlen(path);
+    request->path.path = qemu_strdup(path);
+    if (credp) {
+        request->data.mode = credp->fc_mode;
+        request->data.uid = credp->fc_uid;
+        request->data.gid = credp->fc_gid;
+        request->data.dev = credp->fc_rdev;
+    }
+}
+
+static int passthrough_open(FsContext *fs_ctx, const char *path, int flags)
+{
+    V9fsFileObjectRequest request;
+    int fd, error = 0;
+
+    fill_request(&request, path, NULL);
+    request.data.flags = flags;
+    request.data.type = T_OPEN;
+    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)
 {
@@ -138,14 +169,27 @@ static int local_closedir(FsContext *ctx, DIR *dir)
     return closedir(dir);
 }
 
-static int local_open(FsContext *ctx, const char *path, int flags)
+static int local_open(FsContext *fs_ctx, const char *path, int flags)
 {
-    return open(rpath(ctx, path), flags);
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        return passthrough_open(fs_ctx, path, flags);
+    } else {
+        return open(rpath(fs_ctx, path), flags);
+    }
 }
 
-static DIR *local_opendir(FsContext *ctx, const char *path)
+static DIR *local_opendir(FsContext *fs_ctx, const char *path)
 {
-    return opendir(rpath(ctx, path));
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        int fd;
+        fd = passthrough_open(fs_ctx, path, O_DIRECTORY);
+        if (fd < 0) {
+            return NULL;
+        }
+        return fdopendir(fd);
+    } else {
+        return opendir(rpath(fs_ctx, path));
+    }
 }
 
 static void local_rewinddir(FsContext *ctx, DIR *dir)
-- 
1.7.3.4