From: Karel Zak <kzak@redhat.com>
Date: Thu, 19 Nov 2020 10:12:06 +0000 (+0100)
Subject: umount: ignore --no-canonicalize,-c for non-root users
X-Git-Tag: v2.36.2~40
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0bfa747f0176af4b94a4e1f6f434ddfcd9ce5099;p=thirdparty%2Futil-linux.git

umount: ignore --no-canonicalize,-c for non-root users

It seems better to ignore this option than drop-permissions and later
exit with EPERMs. This change makes umount(8) more compatible with
fuser user umounts by systemd where -c is used to reduce overhead etc.

Addresses: https://github.com/karelzak/util-linux/issues/1192
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/sys-utils/umount.8 b/sys-utils/umount.8
index a66d11961d..a7f6b12e03 100644
--- a/sys-utils/umount.8
+++ b/sys-utils/umount.8
@@ -89,6 +89,10 @@ system calls. These system calls may hang in some cases (for example on NFS if
 server is not available). The option has to be used with canonical path to the
 mount point.
 
+This option is silently ignored by
+.B umount
+for non-root users.
+
 For more details about this option see the
 .BR mount (8)
 man page. Note that \fBumount\fR does not pass this option to the
diff --git a/sys-utils/umount.c b/sys-utils/umount.c
index 056ffb895a..8b7e1ddea3 100644
--- a/sys-utils/umount.c
+++ b/sys-utils/umount.c
@@ -504,8 +504,17 @@ int main(int argc, char **argv)
 
 
 		/* only few options are allowed for non-root users */
-		if (mnt_context_is_restricted(cxt) && !strchr("hdilqVv", c))
+		if (mnt_context_is_restricted(cxt) && !strchr("hdilqVv", c)) {
+
+			/* Silently ignore options without direct impact to the
+			 * umount operation, but with security sensitive
+			 * side-effects */
+			if (strchr("c", c))
+				continue;	/* ignore */
+
+			/* drop permissions, continue as regular user */
 			suid_drop(cxt);
+		}
 
 		err_exclusive_options(c, longopts, excl, excl_st);