From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 19 Mar 2024 14:36:53 +0000 (-0400)
Subject: mempool: Use MADV_DONTFORK on init values
X-Git-Url: https://git.efficios.com/?a=commitdiff_plain;h=7f6667b5bc802d30c006207f2d0cc2d025e47d08;p=librseq.git

mempool: Use MADV_DONTFORK on init values

The init values shared mapping should not be shared across fork. Use
madvise MADV_DONTFORK on the memory range to ensure those pages are not
shared with children processes across fork.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I4b3541d21401227ca568ef6e8105d088746341cb
---

diff --git a/src/rseq-mempool.c b/src/rseq-mempool.c
index 1d87e1a..fa1cff0 100644
--- a/src/rseq-mempool.c
+++ b/src/rseq-mempool.c
@@ -748,6 +748,12 @@ struct rseq_mempool_range *rseq_mempool_range_create(struct rseq_mempool *pool)
 				MAP_SHARED | MAP_FIXED, memfd, 0) != (void *) range->init) {
 			goto error_alloc;
 		}
+		/*
+		 * Make sure the init values shared mapping is not
+		 * shared with the children processes across fork.
+		 */
+		if (madvise(range->init, pool->attr.stride, MADV_DONTFORK))
+			goto error_alloc;
 		assert(pool->attr.type == MEMPOOL_TYPE_PERCPU);
 		/*
 		 * Map per-cpu memory as private COW mappings of init values.