From be68e94f81d8bb830cfda6eee6a20a41ec335933 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Thu, 9 Jul 2026 15:51:30 +0300 Subject: [PATCH 1/1] 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 Discussion: https://www.postgresql.org/message-id/34844e8c-267c-4daf-b1e0-f26059a4a7d3@eisentraut.org --- 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 dd772838005..f11b58bf9c7 100644 --- a/src/interfaces/libpq/fe-misc.c +++ b/src/interfaces/libpq/fe-misc.c @@ -928,13 +928,18 @@ 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 70faf8b2fe0..1a8e2e6746e 100644 --- a/src/interfaces/libpq/fe-secure.c +++ b/src/interfaces/libpq/fe-secure.c @@ -247,8 +247,9 @@ 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) -- 2.47.3