cifs: Fix handling of a beyond-EOF DIO/unbuffered read over SMB2

[ Upstream commit 4ae4dde6f34a4124c65468ae4fa1f915fb40f900 ]

If a DIO read or an unbuffered read request extends beyond the EOF, the
server will return a short read and a status code indicating that EOF was
hit, which gets translated to -ENODATA.  Note that the client does not cap
the request at i_size, but asks for the amount requested in case there's a
race on the server with a third party.

Now, on the client side, the request will get split into multiple
subrequests if rsize is smaller than the full request size.  A subrequest
that starts before or at the EOF and returns short data up to the EOF will
be correctly handled, with the NETFS_SREQ_HIT_EOF flag being set,
indicating to netfslib that we can't read more.

If a subrequest, however, starts after the EOF and not at it, HIT_EOF will
not be flagged, its error will be set to -ENODATA and it will be abandoned.
This will cause the request as a whole to fail with -ENODATA.

Fix this by setting NETFS_SREQ_HIT_EOF on any subrequest that lies beyond
the EOF marker.

Fixes: 1da29f2c39b6 ("netfs, cifs: Fix handling of short DIO read")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 8b4a4573e9c372478af9b2c10525e0656f53a1b9..e661d40213eabc830009b22a7d175a208cbc1090 100644 (file)
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -4629,7 +4629,7 @@ do_retry:
        } else {
                size_t trans = rdata->subreq.transferred + rdata->got_bytes;
                if (trans < rdata->subreq.len &&
-                   rdata->subreq.start + trans == ictx->remote_i_size) {
+                   rdata->subreq.start + trans >= ictx->remote_i_size) {
                        __set_bit(NETFS_SREQ_HIT_EOF, &rdata->subreq.flags);
                        rdata->result = 0;
                }