linux-kernel - [PATCH v2 11/16] device-mapper: "." and ".." are not valid symlink names

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Message-Id: <20230530203116.2008-12-demi@invisiblethingslab.com>
Date:   Tue, 30 May 2023 16:31:11 -0400
From:   Demi Marie Obenour <demi@...isiblethingslab.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Roger Pau Monné <roger.pau@...rix.com>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com
Cc:     Demi Marie Obenour <demi@...isiblethingslab.com>,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Subject: [PATCH v2 11/16] device-mapper: "." and ".." are not valid symlink names

Using either of these is going to greatly confuse userspace, as they are
not valid symlink names and so creating the usual /dev/mapper/NAME
symlink will not be possible.  As creating a device with either of these
names is almost certainly a userspace bug, just error out.

Signed-off-by: Demi Marie Obenour <demi@...isiblethingslab.com>
---
 drivers/md/dm-ioctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 9ae00e3c1a72c19575814cf473774835b364320b..17ece816d490b6c40d019da131ade44c9a201dab 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -775,8 +775,10 @@ static int check_name(const char *name)
 		return -EINVAL;
 	}
 
-	if (strcmp(name, DM_CONTROL_NODE) == 0) {
-		DMERR("device name cannot be \"%s\"", DM_CONTROL_NODE);
+	if (strcmp(name, DM_CONTROL_NODE) == 0 ||
+	    strcmp(name, ".") == 0 ||
+	    strcmp(name, "..") == 0) {
+		DMERR("device name cannot be \"%s\", \".\", or \"..\"", DM_CONTROL_NODE);
 		return -EINVAL;
 	}
 
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab