From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:01:16 +0000

Subject: [PATCH] virtiofsd: passthrough_ll: add fd_map to hide file

 descriptors

Do not expose file descriptor numbers to clients.  This prevents the

abuse of internal file descriptors (like stdin/stdout).

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

Fix from:

Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>

dgilbert:

  Added lseek

Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

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

(cherry picked from commit 73b4d19dfc4248a74c1f3e511cfa934681d9c602)

---

 tools/virtiofsd/passthrough_ll.c | 116 +++++++++++++++++++++++++------

 1 file changed, 94 insertions(+), 22 deletions(-)

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

index 5f5a72fdbb..9815bfa5c5 100644

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

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

@@ -60,6 +60,7 @@ struct lo_map_elem {

     union {

         struct lo_inode *inode;

         struct lo_dirp *dirp;

+        int fd;

         ssize_t freelist;

     };

     bool in_use;

@@ -107,6 +108,7 @@ struct lo_data {

     struct lo_inode root; /* protected by lo->mutex */

     struct lo_map ino_map; /* protected by lo->mutex */

     struct lo_map dirp_map; /* protected by lo->mutex */

+    struct lo_map fd_map; /* protected by lo->mutex */

 };

 static const struct fuse_opt lo_opts[] = {

@@ -236,6 +238,20 @@ static void lo_map_remove(struct lo_map *map, size_t key)

     map->freelist = key;

 }

+/* Assumes lo->mutex is held */

+static ssize_t lo_add_fd_mapping(fuse_req_t req, int fd)

+{

+    struct lo_map_elem *elem;

+

+    elem = lo_map_alloc_elem(&lo_data(req)->fd_map);

+    if (!elem) {

+        return -1;

+    }

+

+    elem->fd = fd;

+    return elem - lo_data(req)->fd_map.elems;

+}

+

 /* Assumes lo->mutex is held */

 static ssize_t lo_add_dirp_mapping(fuse_req_t req, struct lo_dirp *dirp)

 {

@@ -350,6 +366,22 @@ static int utimensat_empty_nofollow(struct lo_inode *inode,

     return utimensat(AT_FDCWD, procname, tv, 0);

 }

+static int lo_fi_fd(fuse_req_t req, struct fuse_file_info *fi)

+{

+    struct lo_data *lo = lo_data(req);

+    struct lo_map_elem *elem;

+

+    pthread_mutex_lock(&lo->mutex);

+    elem = lo_map_get(&lo->fd_map, fi->fh);

+    pthread_mutex_unlock(&lo->mutex);

+

+    if (!elem) {

+        return -1;

+    }

+

+    return elem->fd;

+}

+

 static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,

                        int valid, struct fuse_file_info *fi)

 {

@@ -358,6 +390,7 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,

     struct lo_inode *inode;

     int ifd;

     int res;

+    int fd;

     inode = lo_inode(req, ino);

     if (!inode) {

@@ -367,9 +400,14 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,

     ifd = inode->fd;

+    /* If fi->fh is invalid we'll report EBADF later */

+    if (fi) {

+        fd = lo_fi_fd(req, fi);

+    }

+

     if (valid & FUSE_SET_ATTR_MODE) {

         if (fi) {

-            res = fchmod(fi->fh, attr->st_mode);

+            res = fchmod(fd, attr->st_mode);

         } else {

             sprintf(procname, "/proc/self/fd/%i", ifd);

             res = chmod(procname, attr->st_mode);

@@ -389,7 +427,7 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,

     }

     if (valid & FUSE_SET_ATTR_SIZE) {

         if (fi) {

-            res = ftruncate(fi->fh, attr->st_size);

+            res = ftruncate(fd, attr->st_size);

         } else {

             sprintf(procname, "/proc/self/fd/%i", ifd);

             res = truncate(procname, attr->st_size);

@@ -419,7 +457,7 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,

         }

         if (fi) {

-            res = futimens(fi->fh, tv);

+            res = futimens(fd, tv);

         } else {

             res = utimensat_empty_nofollow(inode, tv);

         }

@@ -1096,7 +1134,18 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,

     lo_restore_cred(&old;;

     if (!err) {

-        fi->fh = fd;

+        ssize_t fh;

+

+        pthread_mutex_lock(&lo->mutex);

+        fh = lo_add_fd_mapping(req, fd);

+        pthread_mutex_unlock(&lo->mutex);

+        if (fh == -1) {

+            close(fd);

+            fuse_reply_err(req, ENOMEM);

+            return;

+        }

+

+        fi->fh = fh;

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

     }

     if (lo->cache == CACHE_NEVER) {

@@ -1140,6 +1189,7 @@ static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync,

 static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)

 {

     int fd;

+    ssize_t fh;

     char buf[64];

     struct lo_data *lo = lo_data(req);

@@ -1175,7 +1225,16 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)

         return (void)fuse_reply_err(req, errno);

     }

-    fi->fh = fd;

+    pthread_mutex_lock(&lo->mutex);

+    fh = lo_add_fd_mapping(req, fd);

+    pthread_mutex_unlock(&lo->mutex);

+    if (fh == -1) {

+        close(fd);

+        fuse_reply_err(req, ENOMEM);

+        return;

+    }

+

+    fi->fh = fh;

     if (lo->cache == CACHE_NEVER) {

         fi->direct_io = 1;

     } else if (lo->cache == CACHE_ALWAYS) {

@@ -1187,9 +1246,18 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)

 static void lo_release(fuse_req_t req, fuse_ino_t ino,

                        struct fuse_file_info *fi)

 {

+    struct lo_data *lo = lo_data(req);

+    int fd;

+

     (void)ino;

-    close(fi->fh);

+    fd = lo_fi_fd(req, fi);

+

+    pthread_mutex_lock(&lo->mutex);

+    lo_map_remove(&lo->fd_map, fi->fh);

+    pthread_mutex_unlock(&lo->mutex);

+

+    close(fd);

     fuse_reply_err(req, 0);

 }

@@ -1197,7 +1265,7 @@ static void lo_flush(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)

 {

     int res;

     (void)ino;

-    res = close(dup(fi->fh));

+    res = close(dup(lo_fi_fd(req, fi)));

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

 }

@@ -1224,7 +1292,7 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,

             return (void)fuse_reply_err(req, errno);

         }

     } else {

-        fd = fi->fh;

+        fd = lo_fi_fd(req, fi);

     }

     if (datasync) {

@@ -1251,7 +1319,7 @@ static void lo_read(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset,

     }

     buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK;

-    buf.buf[0].fd = fi->fh;

+    buf.buf[0].fd = lo_fi_fd(req, fi);

     buf.buf[0].pos = offset;

     fuse_reply_data(req, &buf;;

@@ -1266,7 +1334,7 @@ static void lo_write_buf(fuse_req_t req, fuse_ino_t ino,

     struct fuse_bufvec out_buf = FUSE_BUFVEC_INIT(fuse_buf_size(in_buf));

     out_buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK;

-    out_buf.buf[0].fd = fi->fh;

+    out_buf.buf[0].fd = lo_fi_fd(req, fi);

     out_buf.buf[0].pos = off;

     if (lo_debug(req)) {

@@ -1303,7 +1371,7 @@ static void lo_fallocate(fuse_req_t req, fuse_ino_t ino, int mode, off_t offset,

     (void)ino;

 #ifdef CONFIG_FALLOCATE

-    err = fallocate(fi->fh, mode, offset, length);

+    err = fallocate(lo_fi_fd(req, fi), mode, offset, length);

     if (err < 0) {

         err = errno;

     }

@@ -1314,7 +1382,7 @@ static void lo_fallocate(fuse_req_t req, fuse_ino_t ino, int mode, off_t offset,

         return;

     }

-    err = posix_fallocate(fi->fh, offset, length);

+    err = posix_fallocate(lo_fi_fd(req, fi), offset, length);

 #endif

     fuse_reply_err(req, err);

@@ -1326,7 +1394,7 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,

     int res;

     (void)ino;

-    res = flock(fi->fh, op);

+    res = flock(lo_fi_fd(req, fi), op);

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

 }

@@ -1551,17 +1619,19 @@ static void lo_copy_file_range(fuse_req_t req, fuse_ino_t ino_in, off_t off_in,

                                off_t off_out, struct fuse_file_info *fi_out,

                                size_t len, int flags)

 {

+    int in_fd, out_fd;

     ssize_t res;

-    if (lo_debug(req))

-        fuse_log(FUSE_LOG_DEBUG,

-                 "lo_copy_file_range(ino=%" PRIu64 "/fd=%lu, "

-                 "off=%lu, ino=%" PRIu64 "/fd=%lu, "

-                 "off=%lu, size=%zd, flags=0x%x)\n",

-                 ino_in, fi_in->fh, off_in, ino_out, fi_out->fh, off_out, len,

-                 flags);

+    in_fd = lo_fi_fd(req, fi_in);

+    out_fd = lo_fi_fd(req, fi_out);

+

+    fuse_log(FUSE_LOG_DEBUG,

+             "lo_copy_file_range(ino=%" PRIu64 "/fd=%d, "

+             "off=%lu, ino=%" PRIu64 "/fd=%d, "

+             "off=%lu, size=%zd, flags=0x%x)\n",

+             ino_in, in_fd, off_in, ino_out, out_fd, off_out, len, flags);

-    res = copy_file_range(fi_in->fh, &off_in, fi_out->fh, &off_out, len, flags);

+    res = copy_file_range(in_fd, &off_in, out_fd, &off_out, len, flags);

     if (res < 0) {

         fuse_reply_err(req, -errno);

     } else {

@@ -1576,7 +1646,7 @@ static void lo_lseek(fuse_req_t req, fuse_ino_t ino, off_t off, int whence,

     off_t res;

     (void)ino;

-    res = lseek(fi->fh, off, whence);

+    res = lseek(lo_fi_fd(req, fi), off, whence);

     if (res != -1) {

         fuse_reply_lseek(req, res);

     } else {

@@ -1661,6 +1731,7 @@ int main(int argc, char *argv[])

     root_elem->inode = &lo.root;

     lo_map_init(&lo.dirp_map);

+    lo_map_init(&lo.fd_map);

     if (fuse_parse_cmdline(&args, &opts) != 0) {

         return 1;

@@ -1758,6 +1829,7 @@ err_out2:

 err_out1:

     fuse_opt_free_args(&args);

+    lo_map_destroy(&lo.fd_map);

     lo_map_destroy(&lo.dirp_map);

     lo_map_destroy(&lo.ino_map);