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Commit1144ea3

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Prevent shm_mq_send from reading uninitialized memory.
shm_mq_send_bytes didn't invariably initialize *bytes_written beforereturning, which would cause shm_mq_send to read from uninitializedmemory and add the value it found there to mqh->mqh_partial_bytes.This could cause the next attempt to send a message via the queue tofail an assertion (if the queue was detached) or copy data from agarbage pointer value into the queue (if non-blocking mode was in use).
1 parent250c26b commit1144ea3

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‎src/backend/storage/ipc/shm_mq.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -676,7 +676,10 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, void *data, bool nowait,
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/* Bail out if the queue has been detached. */
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if (detached)
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{
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*bytes_written=sent;
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returnSHM_MQ_DETACHED;
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}
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if (available==0)
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{
@@ -691,12 +694,16 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, void *data, bool nowait,
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if (nowait)
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{
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if (shm_mq_get_receiver(mq)==NULL)
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{
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*bytes_written=sent;
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returnSHM_MQ_WOULD_BLOCK;
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}
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}
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elseif (!shm_mq_wait_internal(mq,&mq->mq_receiver,
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mqh->mqh_handle))
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{
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mq->mq_detached= true;
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*bytes_written=sent;
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returnSHM_MQ_DETACHED;
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}
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mqh->mqh_counterparty_attached= true;

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