lib/vfscore: Linux compatibility for sys_utimensat

Previously, if pathname is either NULL or a relative path, and
dirfd is not AT_FDCWD, dirfd needed to refer to a directory.
However, in Linux there is a non-conformant behavior that
if pathname is NULL, the timestamps are applied to whatever
file dirfd refers to. For improved Linux compatibility, we
adopt this behavior.

This commit also fixes various leaks of the file descriptor
reference that is received via the call to vfscore_get_file().

Github-Fixes: #858
Signed-off-by: Marc Rittinghaus <marc.rittinghaus@unikraft.io>
Reviewed-by: Stefan Jumarea <stefanjumarea02@gmail.com>
Reviewed-by: Rares Miculescu <miculescur@gmail.com>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #865

diff --git a/lib/vfscore/syscalls.c b/lib/vfscore/syscalls.c
index 923f3d409604a3e7cc7ed8828adb4493a3fe3585..830b76e0c749f12ad885077f547df1a06089ae3c 100644 (file)
--- a/lib/vfscore/syscalls.c
+++ b/lib/vfscore/syscalls.c
@@ -1398,7 +1398,8 @@ sys_utimensat(int dirfd, const char *pathname, const struct timespec times[2], i
        char *ap;
        struct timespec timespec_times[2];
        extern struct task *main_task;
-       struct dentry *dp;
+       struct dentry *dp = NULL;
+       struct vfscore_file *fp = NULL;
 
        /* utimensat should return ENOENT when pathname is empty */
        if(pathname && pathname[0] == 0)
@@ -1425,8 +1426,6 @@ sys_utimensat(int dirfd, const char *pathname, const struct timespec times[2], i
                if (unlikely(error == -1))
                        return ENOMEM;
        } else {
-               struct vfscore_file *fp;
-
                fp = vfscore_get_file(dirfd);
                if (!fp)
                        return EBADF;
@@ -1434,26 +1433,43 @@ sys_utimensat(int dirfd, const char *pathname, const struct timespec times[2], i
                if (!fp->f_dentry)
                        return EBADF;
 
-               if (!(fp->f_dentry->d_vnode->v_type & VDIR))
-                       return ENOTDIR;
+               if (pathname) {
+                       if (unlikely(!(fp->f_dentry->d_vnode->v_type & VDIR))) {
+                               fdrop(fp);
+                               return ENOTDIR;
+                       }
 
-               if (pathname)
-                       error = asprintf(&ap, "%s/%s/%s", fp->f_dentry->d_mount->m_path,
-                                       fp->f_dentry->d_path, pathname);
-               else
-                       error = asprintf(&ap, "%s/%s", fp->f_dentry->d_mount->m_path,
-                                       fp->f_dentry->d_path);
-               if (unlikely(error == -1))
-                       return ENOMEM;
+                       error = asprintf(&ap, "%s/%s/%s",
+                                        fp->f_dentry->d_mount->m_path,
+                                        fp->f_dentry->d_path, pathname);
+
+                       fdrop(fp);
+                       fp = NULL;
+
+                       if (unlikely(error == -1))
+                               return ENOMEM;
+               } else {
+                       /* On Linux, if pathname is NULL dirfd does not need to
+                        * be a directory. The change is applied to whatever
+                        * file dirfd refers to.
+                        */
+                       dp = fp->f_dentry;
+               }
        }
 
-       /* FIXME: Add support for AT_SYMLINK_NOFOLLOW */
+       if (!dp) {
+               UK_ASSERT(!fp);
+               UK_ASSERT(ap);
 
-       error = namei(ap, &dp);
-       free(ap);
+               /* FIXME: Add support for AT_SYMLINK_NOFOLLOW */
+               error = namei(ap, &dp);
+               free(ap);
 
-       if (error)
-               return error;
+               if (unlikely(error))
+                       return error;
+
+               UK_ASSERT(dp);
+       }
 
        if (dp->d_mount->m_flags & MNT_RDONLY) {
                error = EROFS;
@@ -1464,7 +1480,12 @@ sys_utimensat(int dirfd, const char *pathname, const struct timespec times[2], i
                error = vn_settimes(dp->d_vnode, timespec_times);
        }
 
-       drele(dp);
+exit_rel:
+       if (fp)
+               fdrop(fp);
+       else
+               drele(dp);
+
        return error;
 }