From 2a0c3a62ea4ad6c6bcbf80122b070f3ff3fe7dae Mon Sep 17 00:00:00 2001 From: Ian Jackson Date: Mon, 24 Feb 2014 14:19:14 +0000 Subject: [PATCH] libxl: Hold the atfork lock while closing carefd This avoids the process being forked while a carefd is recorded in the list but the actual fd has been closed. If that happened, a subsequent libxl_postfork_child_noexec would attempt to close the fd again. If we are lucky that results in a harmless warning; but if we are unlucky the fd number has been reused and we close an unrelated fd. This race has not been observed anywhere as far as we are aware. Signed-off-by: Ian Jackson Acked-by: Ian Campbell CC: George Dunlap --- tools/libxl/libxl_fork.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/libxl/libxl_fork.c b/tools/libxl/libxl_fork.c index 8421296d8d..fa150959ad 100644 --- a/tools/libxl/libxl_fork.c +++ b/tools/libxl/libxl_fork.c @@ -184,9 +184,9 @@ void libxl_postfork_child_noexec(libxl_ctx *ctx) int libxl__carefd_close(libxl__carefd *cf) { if (!cf) return 0; + atfork_lock(); int r = cf->fd < 0 ? 0 : close(cf->fd); int esave = errno; - atfork_lock(); LIBXL_LIST_REMOVE(cf, entry); atfork_unlock(); free(cf); -- 2.30.2