From: Robert Haas Date: Thu, 6 Aug 2015 17:25:45 +0000 (-0400) Subject: Fix incorrect calculation in shm_mq_receive. X-Git-Tag: REL9_4_5~99 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e72f2115ef6d574c64f42ea8b4cbe96accee08b2;p=postgresql Fix incorrect calculation in shm_mq_receive. If some, but not all, of the length word has already been read, and the next attempt to read sees exactly the number of bytes needed to complete the length word, or fewer, then we'll incorrectly read less than all of the available data. Antonin Houska --- diff --git a/src/backend/storage/ipc/shm_mq.c b/src/backend/storage/ipc/shm_mq.c index d96627a774..a49bd17fee 100644 --- a/src/backend/storage/ipc/shm_mq.c +++ b/src/backend/storage/ipc/shm_mq.c @@ -488,7 +488,7 @@ shm_mq_receive(shm_mq_handle *mqh, Size *nbytesp, void **datap, bool nowait) if (mqh->mqh_partial_bytes + rb > sizeof(Size)) lengthbytes = sizeof(Size) - mqh->mqh_partial_bytes; else - lengthbytes = rb - mqh->mqh_partial_bytes; + lengthbytes = rb; memcpy(&mqh->mqh_buffer[mqh->mqh_partial_bytes], rawdata, lengthbytes); mqh->mqh_partial_bytes += lengthbytes;