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Commit eec7ef60 authored by David Howells's avatar David Howells Committed by Greg Kroah-Hartman
Browse files

afs: Fix dynamic root lookup DNS check 



[ Upstream commit 74cef6872ceaefb5b6c5c60641371ea28702d358 ]

In the afs dynamic root directory, the ->lookup() function does a DNS check
on the cell being asked for and if the DNS upcall reports an error it will
report an error back to userspace (typically ENOENT).

However, if a failed DNS upcall returns a new-style result, it will return
a valid result, with the status field set appropriately to indicate the
type of failure - and in that case, dns_query() doesn't return an error and
we let stat() complete with no error - which can cause confusion in
userspace as subsequent calls that trigger d_automount then fail with
ENOENT.

Fix this by checking the status result from a valid dns_query() and
returning an error if it indicates a failure.

Fixes: bbb4c432 ("dns: Allow the dns resolver to retrieve a server set")
Reported-by: default avatarMarkus Suvanto <markus.suvanto@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=216637


Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Tested-by: default avatarMarkus Suvanto <markus.suvanto@gmail.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 82d64cbe

fs/afs/dynroot.c

+16 −2
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ static int afs_probe_cell_name(struct dentry *dentry) 
	struct afs_net *net = afs_d2net(dentry);

	const char *name = dentry->d_name.name;

	size_t len = dentry->d_name.len;

	char *result = NULL;

	int ret;



	/* Names prefixed with a dot are R/W mounts. */
@@ -37,9 +38,22 @@ static int afs_probe_cell_name(struct dentry *dentry) 
	}



	ret = dns_query(net->net, "afsdb", name, len, "srv=1",

			NULL, NULL, false);

	if (ret == -ENODATA || ret == -ENOKEY)

			&result, NULL, false);

	if (ret == -ENODATA || ret == -ENOKEY || ret == 0)

		ret = -ENOENT;

	if (ret > 0 && ret >= sizeof(struct dns_server_list_v1_header)) {

		struct dns_server_list_v1_header *v1 = (void *)result;



		if (v1->hdr.zero == 0 &&

		    v1->hdr.content == DNS_PAYLOAD_IS_SERVER_LIST &&

		    v1->hdr.version == 1 &&

		    (v1->status != DNS_LOOKUP_GOOD &&

		     v1->status != DNS_LOOKUP_GOOD_WITH_BAD))

			return -ENOENT;



	}



	kfree(result);

	return ret;

}