From: Norman Wilson <norman@teach.cs.toronto.edu>
Date: Mon, 12 Aug 2024 18:16:30 +0000 (-0400)
Subject: Rearrange util/fusermount.c umount_fuse_locked() so that
X-Git-Tag: fuse-3.17.1-rc0~79
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c9bf7d3e20ec5c86dd590f695b92e65142491d0e;p=qemu-gpiodev%2Flibfuse.git

Rearrange util/fusermount.c umount_fuse_locked() so that
umount2 is called with privs dropped, not raised.  This
works around a clash with NFS permissions: if FUSE mounted
on NFS client directory with root_squash in effect, and
some directory in the path leading to the mount point denies
permissions to others, umount2 will fail because userid 0
cannot search it.  Since drop_privs merely sets the file-
system user- and group-ID without changing the CAP_SYS_ADMIN
capability needed to unmount a file system (which fusermount
has because it is set-user-ID root), umount2 works fine.
---

diff --git a/util/fusermount.c b/util/fusermount.c
index e40c457..f37c616 100644
--- a/util/fusermount.c
+++ b/util/fusermount.c
@@ -523,11 +523,13 @@ static int unmount_fuse_locked(const char *mnt, int quiet, int lazy)
 
 	drop_privs();
 	res = chdir_to_parent(copy, &last);
-	restore_privs();
-	if (res == -1)
+	if (res == -1) {
+		restore_privs();
 		goto out;
+	}
 
 	res = umount2(last, umount_flags);
+	restore_privs();
 	if (res == -1 && !quiet) {
 		fprintf(stderr, "%s: failed to unmount %s: %s\n",
 			progname, mnt, strerror(errno));