[PATCH v4 07/12] virtiofsd: Let lo_inode_open() return a TempFd

[Hanna Reitz <hreitz@redhat.com>]

Strictly speaking, this is not necessary, because lo_inode_open() will
always return a new FD owned by the caller, so TempFd.owned will always
be true.

The auto-cleanup is nice, though.  Also, we get a more unified interface
where you always get a TempFd when you need an FD for an lo_inode
(regardless of whether it is an O_PATH FD or a non-O_PATH FD).

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
 tools/virtiofsd/passthrough_ll.c | 156 +++++++++++++++----------------
 1 file changed, 75 insertions(+), 81 deletions(-)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 3bf20b8659..d257eda129 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -293,10 +293,8 @@ static void temp_fd_clear(TempFd *temp_fd)
 /**
  * Return an owned fd from *temp_fd that will not be closed when
  * *temp_fd goes out of scope.
- *
- * (TODO: Remove __attribute__ once this is used.)
  */
-static __attribute__((unused)) int temp_fd_steal(TempFd *temp_fd)
+static int temp_fd_steal(TempFd *temp_fd)
 {
     if (temp_fd->owned) {
         temp_fd->owned = false;
@@ -309,10 +307,8 @@ static __attribute__((unused)) int temp_fd_steal(TempFd *temp_fd)
 /**
  * Create a borrowing copy of an existing TempFd.  Note that *to is
  * only valid as long as *from is valid.
- *
- * (TODO: Remove __attribute__ once this is used.)
  */
-static __attribute__((unused)) void temp_fd_copy(const TempFd *from, TempFd *to)
+static void temp_fd_copy(const TempFd *from, TempFd *to)
 {
     *to = (TempFd) {
         .fd = from->fd,
@@ -689,9 +685,12 @@ static int lo_fd(fuse_req_t req, fuse_ino_t ino, TempFd *tfd)
  * when a malicious client opens special files such as block device nodes.
  * Symlink inodes are also rejected since symlinks must already have been
  * traversed on the client side.
+ *
+ * The fd is returned in tfd->fd.  The return value is 0 on success and -errno
+ * otherwise.
  */
 static int lo_inode_open(struct lo_data *lo, struct lo_inode *inode,
-                         int open_flags)
+                         int open_flags, TempFd *tfd)
 {
     g_autofree char *fd_str = g_strdup_printf("%d", inode->fd);
     int fd;
@@ -710,7 +709,13 @@ static int lo_inode_open(struct lo_data *lo, struct lo_inode *inode,
     if (fd < 0) {
         return -errno;
     }
-    return fd;
+
+    *tfd = (TempFd) {
+        .fd = fd,
+        .owned = true,
+    };
+
+    return 0;
 }
 
 static void lo_init(void *userdata, struct fuse_conn_info *conn)
@@ -854,7 +859,8 @@ static int lo_fi_fd(fuse_req_t req, struct fuse_file_info *fi)
 static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
                        int valid, struct fuse_file_info *fi)
 {
-    g_auto(TempFd) path_fd = TEMP_FD_INIT;
+    g_auto(TempFd) path_fd = TEMP_FD_INIT; /* at least an O_PATH fd */
+    g_auto(TempFd) rw_fd = TEMP_FD_INIT; /* O_RDWR fd */
     int saverr;
     char procname[64];
     struct lo_data *lo = lo_data(req);
@@ -868,7 +874,15 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
         return;
     }
 
-    res = lo_inode_fd(inode, &path_fd);
+    if (!fi && (valid & FUSE_SET_ATTR_SIZE)) {
+        /* We need an O_RDWR FD for ftruncate() */
+        res = lo_inode_open(lo, inode, O_RDWR, &rw_fd);
+        if (res >= 0) {
+            temp_fd_copy(&rw_fd, &path_fd);
+        }
+    } else {
+        res = lo_inode_fd(inode, &path_fd);
+    }
     if (res < 0) {
         saverr = -res;
         goto out_err;
@@ -916,18 +930,12 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
         if (fi) {
             truncfd = fd;
         } else {
-            truncfd = lo_inode_open(lo, inode, O_RDWR);
-            if (truncfd < 0) {
-                saverr = -truncfd;
-                goto out_err;
-            }
+            assert(rw_fd.fd >= 0);
+            truncfd = rw_fd.fd;
         }
 
         saverr = drop_security_capability(lo, truncfd);
         if (saverr) {
-            if (!fi) {
-                close(truncfd);
-            }
             goto out_err;
         }
 
@@ -935,9 +943,6 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
             res = drop_effective_cap("FSETID", &cap_fsetid_dropped);
             if (res != 0) {
                 saverr = res;
-                if (!fi) {
-                    close(truncfd);
-                }
                 goto out_err;
             }
         }
@@ -950,9 +955,6 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
                 fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_FSETID\n");
             }
         }
-        if (!fi) {
-            close(truncfd);
-        }
         if (res == -1) {
             goto out_err;
         }
@@ -1840,11 +1842,13 @@ static struct lo_dirp *lo_dirp(fuse_req_t req, struct fuse_file_info *fi)
 static void lo_opendir(fuse_req_t req, fuse_ino_t ino,
                        struct fuse_file_info *fi)
 {
+    g_auto(TempFd) rd_fd = TEMP_FD_INIT;
     int error = ENOMEM;
     struct lo_data *lo = lo_data(req);
     struct lo_inode *inode;
     struct lo_dirp *d = NULL;
     int fd;
+    int res;
     ssize_t fh;
 
     inode = lo_inode(req, ino);
@@ -1858,14 +1862,16 @@ static void lo_opendir(fuse_req_t req, fuse_ino_t ino,
         goto out_err;
     }
 
-    fd = lo_inode_open(lo, inode, O_RDONLY);
-    if (fd < 0) {
-        error = -fd;
+    res = lo_inode_open(lo, inode, O_RDONLY, &rd_fd);
+    if (res < 0) {
+        error = -res;
         goto out_err;
     }
 
+    fd = temp_fd_steal(&rd_fd);
     d->dp = fdopendir(fd);
     if (d->dp == NULL) {
+        close(fd);
         goto out_errno;
     }
 
@@ -1895,8 +1901,6 @@ out_err:
     if (d) {
         if (d->dp) {
             closedir(d->dp);
-        } else if (fd != -1) {
-            close(fd);
         }
         free(d);
     }
@@ -2096,6 +2100,7 @@ static void update_open_flags(int writeback, int allow_direct_io,
 static int lo_do_open(struct lo_data *lo, struct lo_inode *inode,
                       int existing_fd, struct fuse_file_info *fi)
 {
+    g_auto(TempFd) opened_fd = TEMP_FD_INIT;
     ssize_t fh;
     int fd = existing_fd;
     int err;
@@ -2112,16 +2117,18 @@ static int lo_do_open(struct lo_data *lo, struct lo_inode *inode,
             }
         }
 
-        fd = lo_inode_open(lo, inode, fi->flags);
+        err = lo_inode_open(lo, inode, fi->flags, &opened_fd);
 
         if (cap_fsetid_dropped) {
             if (gain_effective_cap("FSETID")) {
                 fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_FSETID\n");
             }
         }
-        if (fd < 0) {
-            return -fd;
+        if (err < 0) {
+            return -err;
         }
+        fd = temp_fd_steal(&opened_fd);
+
         if (fi->flags & (O_TRUNC)) {
             int err = drop_security_capability(lo, fd);
             if (err) {
@@ -2231,8 +2238,9 @@ static struct lo_inode_plock *lookup_create_plock_ctx(struct lo_data *lo,
                                                       uint64_t lock_owner,
                                                       pid_t pid, int *err)
 {
+    g_auto(TempFd) rw_fd = TEMP_FD_INIT;
     struct lo_inode_plock *plock;
-    int fd;
+    int res;
 
     plock =
         g_hash_table_lookup(inode->posix_locks, GUINT_TO_POINTER(lock_owner));
@@ -2249,15 +2257,15 @@ static struct lo_inode_plock *lookup_create_plock_ctx(struct lo_data *lo,
 
     /* Open another instance of file which can be used for ofd locks. */
     /* TODO: What if file is not writable? */
-    fd = lo_inode_open(lo, inode, O_RDWR);
-    if (fd < 0) {
-        *err = -fd;
+    res = lo_inode_open(lo, inode, O_RDWR, &rw_fd);
+    if (res < 0) {
+        *err = -res;
         free(plock);
         return NULL;
     }
 
     plock->lock_owner = lock_owner;
-    plock->fd = fd;
+    plock->fd = temp_fd_steal(&rw_fd);
     g_hash_table_insert(inode->posix_locks, GUINT_TO_POINTER(plock->lock_owner),
                         plock);
     return plock;
@@ -2473,6 +2481,7 @@ static void lo_flush(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
 static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
                      struct fuse_file_info *fi)
 {
+    g_auto(TempFd) rw_fd = TEMP_FD_INIT;
     struct lo_inode *inode = lo_inode(req, ino);
     struct lo_data *lo = lo_data(req);
     int res;
@@ -2487,11 +2496,12 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
     }
 
     if (!fi) {
-        fd = lo_inode_open(lo, inode, O_RDWR);
-        if (fd < 0) {
-            res = -fd;
+        res = lo_inode_open(lo, inode, O_RDWR, &rw_fd);
+        if (res < 0) {
+            res = -res;
             goto out;
         }
+        fd = rw_fd.fd;
     } else {
         fd = lo_fi_fd(req, fi);
     }
@@ -2501,9 +2511,6 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
     } else {
         res = fsync(fd) == -1 ? errno : 0;
     }
-    if (!fi) {
-        close(fd);
-    }
 out:
     lo_inode_put(lo, &inode);
     fuse_reply_err(req, res);
@@ -3065,7 +3072,6 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
     struct lo_inode *inode;
     ssize_t ret;
     int saverr;
-    int fd = -1;
 
     if (block_xattr(lo, in_name)) {
         fuse_reply_err(req, EOPNOTSUPP);
@@ -3117,12 +3123,14 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
      * Otherwise, call fchdir() to avoid open().
      */
     if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
-        fd = lo_inode_open(lo, inode, O_RDONLY);
-        if (fd < 0) {
-            saverr = -fd;
+        g_auto(TempFd) rd_fd = TEMP_FD_INIT;
+
+        ret = lo_inode_open(lo, inode, O_RDONLY, &rd_fd);
+        if (ret < 0) {
+            saverr = -ret;
             goto out;
         }
-        ret = fgetxattr(fd, name, value, size);
+        ret = fgetxattr(rd_fd.fd, name, value, size);
         saverr = ret == -1 ? errno : 0;
     } else {
         g_auto(TempFd) path_fd = TEMP_FD_INIT;
@@ -3153,10 +3161,6 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
         fuse_reply_xattr(req, ret);
     }
 out_free:
-    if (fd >= 0) {
-        close(fd);
-    }
-
     lo_inode_put(lo, &inode);
     return;
 
@@ -3176,7 +3180,6 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
     struct lo_inode *inode;
     ssize_t ret;
     int saverr;
-    int fd = -1;
 
     inode = lo_inode(req, ino);
     if (!inode) {
@@ -3200,12 +3203,14 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
     }
 
     if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
-        fd = lo_inode_open(lo, inode, O_RDONLY);
-        if (fd < 0) {
-            saverr = -fd;
+        g_auto(TempFd) rd_fd = TEMP_FD_INIT;
+
+        ret = lo_inode_open(lo, inode, O_RDONLY, &rd_fd);
+        if (ret < 0) {
+            saverr = -ret;
             goto out;
         }
-        ret = flistxattr(fd, value, size);
+        ret = flistxattr(rd_fd.fd, value, size);
         saverr = ret == -1 ? errno : 0;
     } else {
         g_auto(TempFd) path_fd = TEMP_FD_INIT;
@@ -3294,10 +3299,6 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
         fuse_reply_xattr(req, ret);
     }
 out_free:
-    if (fd >= 0) {
-        close(fd);
-    }
-
     lo_inode_put(lo, &inode);
     return;
 
@@ -3312,14 +3313,14 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
                         const char *value, size_t size, int flags,
                         uint32_t extra_flags)
 {
-    g_auto(TempFd) path_fd = TEMP_FD_INIT;
+    g_auto(TempFd) path_fd = TEMP_FD_INIT; /* O_PATH fd */
+    g_auto(TempFd) rd_fd = TEMP_FD_INIT; /* O_RDONLY fd */
     const char *name;
     char *mapped_name;
     struct lo_data *lo = lo_data(req);
     struct lo_inode *inode;
     ssize_t ret;
     int saverr;
-    int fd = -1;
     bool switched_creds = false;
     bool cap_fsetid_dropped = false;
     struct lo_cred old = {};
@@ -3364,9 +3365,9 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
      * setxattr() on the link's filename there.
      */
     if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
-        fd = lo_inode_open(lo, inode, O_RDONLY);
-        if (fd < 0) {
-            saverr = -fd;
+        ret = lo_inode_open(lo, inode, O_RDONLY, &rd_fd);
+        if (ret < 0) {
+            saverr = -ret;
             goto out;
         }
     } else {
@@ -3401,8 +3402,8 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
         }
         switched_creds = true;
     }
-    if (fd >= 0) {
-        ret = fsetxattr(fd, name, value, size, flags);
+    if (rd_fd.fd >= 0) {
+        ret = fsetxattr(rd_fd.fd, name, value, size, flags);
         saverr = ret == -1 ? errno : 0;
     } else {
         char procname[64];
@@ -3424,10 +3425,6 @@ out:
         FCHDIR_NOFAIL(lo->root.fd);
     }
 
-    if (fd >= 0) {
-        close(fd);
-    }
-
     lo_inode_put(lo, &inode);
     g_free(mapped_name);
     fuse_reply_err(req, saverr);
@@ -3442,7 +3439,6 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *in_name)
     struct lo_inode *inode;
     ssize_t ret;
     int saverr;
-    int fd = -1;
 
     if (block_xattr(lo, in_name)) {
         fuse_reply_err(req, EOPNOTSUPP);
@@ -3478,12 +3474,14 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *in_name)
              name);
 
     if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
-        fd = lo_inode_open(lo, inode, O_RDONLY);
-        if (fd < 0) {
-            saverr = -fd;
+        g_auto(TempFd) rd_fd = TEMP_FD_INIT;
+
+        ret = lo_inode_open(lo, inode, O_RDONLY, &rd_fd);
+        if (ret < 0) {
+            saverr = -ret;
             goto out;
         }
-        ret = fremovexattr(fd, name);
+        ret = fremovexattr(rd_fd.fd, name);
         saverr = ret == -1 ? errno : 0;
     } else {
         g_auto(TempFd) path_fd = TEMP_FD_INIT;
@@ -3502,10 +3500,6 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *in_name)
     }
 
 out:
-    if (fd >= 0) {
-        close(fd);
-    }
-
     lo_inode_put(lo, &inode);
     g_free(mapped_name);
     fuse_reply_err(req, saverr);
-- 
2.31.1