Does blockd intentionally skip mounts if device name exists in / ?

[David Adair]

This will block autofs from mounting volumes with names like "home" or "usr" -- was that
actually the intent ?

root at OpenWrt:/# touch /cv
root at OpenWrt:/# ls /mnt/cv
ls: /mnt/cv: No such file or directory
root at OpenWrt:/# rm /cv
root at OpenWrt:/# ls /mnt/cv
[  205.014819] EXT4-fs (dm-3): mounted filesystem with ordered data mode. Opts: 
hi          keepme      lost+found  tt

root at OpenWrt:~# cat /proc/2520/cmdline && echo -n " " && ls -l /proc/2520/cwd
/sbin/blockd lrwxrwxrwx    1 root     root             0 Jun  3 00:01 /proc/2520/cwd -> /

Blockd does not forward mount request to block because of the lstat:

        ULOG_ERR("kernel is requesting a mount -> %s\n", pkt->name);
	if (lstat(pkt->name, &st) == -1)
		if (block("autofs", "add", (char *)pkt->name))
			cmd = AUTOFS_IOC_FAIL;

It seems like the intention was to check either /mnt or /tmp/run/blockd instead of / .
Since /mnt contains symlinks for mounts with the "autofs" property and directories
for anon mounts it seems to make sense but lstat will only work in /tmp/run/blockd.

Perhaps:
        ULOG_ERR("kernel is requesting a mount -> %s\n", pkt->name);
	if (asprintf(&mnt, "/mnt/%s", pkt->name) == -1)
		exit(ENOMEM);
	if (stat(mnt, &st) == -1)
		if (block("autofs", "add", (char *)pkt->name))
			cmd = AUTOFS_IOC_FAIL;
	free(mnt);

Or:  ( haven't tested this one )
        ULOG_ERR("kernel is requesting a mount -> %s\n", pkt->name);
	if (asprintf(&mnt, "/mnt/%s", pkt->name) == -1)
		exit(ENOMEM);
	if (!lstat(pkt->name, &st) && S_ISLNK(st.st_mode))
		if (block("autofs", "add", (char *)pkt->name))
			cmd = AUTOFS_IOC_FAIL;
	free(mnt);

Or just no test at all since there has effectively been no test for years.