[PATCH v6 22/24] netfs: Check for too much data being read

[David Howells <dhowells@redhat.com>]

Put in a check in read subreq termination to detect more data being read
for a subrequest than was requested.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/read_collect.c      | 18 ++++++++++++++++++
 include/trace/events/netfs.h |  1 +
 2 files changed, 19 insertions(+)

diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index 802d1c40cce5..c0170f80d67f 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -227,6 +227,8 @@ static void netfs_collect_read_results(struct netfs_io_request *rreq)
 			notes |= HIT_PENDING;
 		smp_rmb(); /* Read counters after IN_PROGRESS flag. */
 		transferred = READ_ONCE(front->transferred);
+		if (transferred > front->len)
+			transferred = front->len;
 
 		/* If we can now collect the next folio, do so.  We don't want
 		 * to defer this as we have to decide whether we need to copy
@@ -543,6 +545,22 @@ void netfs_read_subreq_terminated(struct netfs_io_subrequest *subreq)
 		break;
 	}
 
+	/* If the subrequest read more than it was supposed to, abort
+	 * the request with EIO as we may have clobbered other parts
+	 * of the buffer that are already read.
+	 */
+	if (subreq->transferred > subreq->len) {
+		trace_netfs_sreq(subreq, netfs_sreq_trace_too_much);
+		__set_bit(NETFS_SREQ_FAILED, &subreq->flags);
+		__clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
+		subreq->transferred = 0;
+		subreq->error = -EIO;
+		trace_netfs_failure(rreq, subreq, subreq->error, netfs_fail_read);
+		trace_netfs_rreq(rreq, netfs_rreq_trace_set_pause);
+		set_bit(NETFS_RREQ_PAUSE, &rreq->flags);
+		goto skip_error_checks;
+	}
+
 	/* Deal with retry requests, short reads and errors.  If we retry
 	 * but don't make progress, we abandon the attempt.
 	 */
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 071d20e80f13..723cb7315308 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -132,6 +132,7 @@
 	EM(netfs_sreq_trace_submit,		"SUBMT")	\
 	EM(netfs_sreq_trace_superfluous,	"SPRFL")	\
 	EM(netfs_sreq_trace_terminated,		"TERM ")	\
+	EM(netfs_sreq_trace_too_much,		"!TOOM")	\
 	EM(netfs_sreq_trace_wait_for,		"_WAIT")	\
 	EM(netfs_sreq_trace_write,		"WRITE")	\
 	EM(netfs_sreq_trace_write_skip,		"SKIP ")	\