postgres.git / summary / log / commit / refs

commit    56988064bcaf91c9526e2b42b19228fc48fff539
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Thu Jul 09 15:34:27 2026 +0000

    libpq: Make error checks in the new buffer draining code more robust
    
    Check explicitly for pqsecure_read() returning an error. It shouldn't
    fail, and we would've caught it in the check for a short read, but
    better to be explicit so that the error message is more informative.
    We also shouldn't update 'inEnd' when the read fails, although that
    too is just pro forma as we will bail out and close the connection on
    error.
    
    Reported-by: Peter Eisentraut <peter@eisentraut.org>
    Discussion: https://www.postgresql.org/message-id/34844e8c-267c-4daf-b1e0-f26059a4a7d3@eisentraut.org
    Backpatch-through: 14


 src/interfaces/libpq/fe-misc.c   | 11 ++++++++---
 src/interfaces/libpq/fe-secure.c |  5 +++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 7e02fcc2452..c5e1d13d6f7 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -914,13 +914,18 @@ pqDrainPending(PGconn *conn)
 
 	nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
 						  bytes_pending);
-	conn->inEnd += nread;
 
-	/* When there are bytes pending, the read function is not supposed to fail */
+	/*
+	 * When there are bytes pending, pqsecure_read() is not supposed to fail
+	 * or do a short read, but let's check anyway to be safe.
+	 */
+	if (nread < 0)
+		return -1;
+	conn->inEnd += nread;
 	if (nread != bytes_pending)
 	{
 		libpq_append_conn_error(conn,
-								"drained only %zu of %zd pending bytes in transport buffer",
+								"drained only %zd of %zd pending bytes in transport buffer",
 								nread, bytes_pending);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 42e8dc0d331..6c48edb983a 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -284,8 +284,9 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
  *	Return the number of bytes available in the transport buffer.
  *
  * If pqsecure_read() is called for this number of bytes, it's guaranteed to
- * return successfully without reading from the underlying socket.  See
- * pqDrainPending() for a more complete discussion of the concepts involved.
+ * return successfully with the same number of bytes, without reading from the
+ * underlying socket.  See pqDrainPending() for a more complete discussion of
+ * the concepts involved.
  */
 ssize_t
 pqsecure_bytes_pending(PGconn *conn)


[parent: 6243ea6c34ac]