From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:01:18 +0000

Subject: [PATCH] virtiofsd: validate path components

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Several FUSE requests contain single path components.  A correct FUSE

client sends well-formed path components but there is currently no input

validation in case something went wrong or the client is malicious.

Refuse ".", "..", and paths containing '/' when we expect a path

component.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit 25dae28c58d7e706b5d5db99042c9db3cef2e657)

---

 tools/virtiofsd/passthrough_ll.c | 59 ++++++++++++++++++++++++++++----

 1 file changed, 53 insertions(+), 6 deletions(-)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c

index ac380efcb1..e375406160 100644

--- a/tools/virtiofsd/passthrough_ll.c

+++ b/tools/virtiofsd/passthrough_ll.c

@@ -133,6 +133,21 @@ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n);

 static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st);

+static int is_dot_or_dotdot(const char *name)

+{

+    return name[0] == '.' &&

+           (name[1] == '\0' || (name[1] == '.' && name[2] == '\0'));

+}

+

+/* Is `path` a single path component that is not "." or ".."? */

+static int is_safe_path_component(const char *path)

+{

+    if (strchr(path, '/')) {

+        return 0;

+    }

+

+    return !is_dot_or_dotdot(path);

+}

 static struct lo_data *lo_data(fuse_req_t req)

 {

@@ -681,6 +696,15 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)

                  parent, name);

     }

+    /*

+     * Don't use is_safe_path_component(), allow "." and ".." for NFS export

+     * support.

+     */

+    if (strchr(name, '/')) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

+

     err = lo_do_lookup(req, parent, name, &e);

     if (err) {

         fuse_reply_err(req, err);

@@ -762,6 +786,11 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,

     struct fuse_entry_param e;

     struct lo_cred old = {};

+    if (!is_safe_path_component(name)) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

+

     dir = lo_inode(req, parent);

     if (!dir) {

         fuse_reply_err(req, EBADF);

@@ -863,6 +892,11 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent,

     struct fuse_entry_param e;

     int saverr;

+    if (!is_safe_path_component(name)) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

+

     inode = lo_inode(req, ino);

     if (!inode) {

         fuse_reply_err(req, EBADF);

@@ -904,6 +938,10 @@ out_err:

 static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name)

 {

     int res;

+    if (!is_safe_path_component(name)) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

     res = unlinkat(lo_fd(req, parent), name, AT_REMOVEDIR);

@@ -916,6 +954,11 @@ static void lo_rename(fuse_req_t req, fuse_ino_t parent, const char *name,

 {

     int res;

+    if (!is_safe_path_component(name) || !is_safe_path_component(newname)) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

+

     if (flags) {

         fuse_reply_err(req, EINVAL);

         return;

@@ -930,6 +973,11 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name)

 {

     int res;

+    if (!is_safe_path_component(name)) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

+

     res = unlinkat(lo_fd(req, parent), name, 0);

     fuse_reply_err(req, res == -1 ? errno : 0);

@@ -1093,12 +1141,6 @@ out_err:

     fuse_reply_err(req, error);

 }

-static int is_dot_or_dotdot(const char *name)

-{

-    return name[0] == '.' &&

-           (name[1] == '\0' || (name[1] == '.' && name[2] == '\0'));

-}

-

 static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,

                           off_t offset, struct fuse_file_info *fi, int plus)

 {

@@ -1248,6 +1290,11 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,

                  parent, name);

     }

+    if (!is_safe_path_component(name)) {

+        fuse_reply_err(req, EINVAL);

+        return;

+    }

+

     err = lo_change_cred(req, &old;;

     if (err) {

         goto out;