5.4-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ 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: bbb4c4323a4d ("dns: Allow the dns resolver to retrieve a server set") Reported-by: Markus Suvanto markus.suvanto@gmail.com Closes: https://bugzilla.kernel.org/show_bug.cgi?id=216637 Signed-off-by: David Howells dhowells@redhat.com Tested-by: Markus Suvanto markus.suvanto@gmail.com cc: Marc Dionne marc.dionne@auristor.com cc: linux-afs@lists.infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/afs/dynroot.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c index f4f2ab6d877f3..d06994990fc35 100644 --- a/fs/afs/dynroot.c +++ b/fs/afs/dynroot.c @@ -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; }