[mdadm,2/2] mdadm: Block SIGCHLD processes before starting children

Commit Message

Logan Gunthorpe June 4, 2024, 4:38 p.m. UTC

There is a small race condition noticed during code review, but
never actully hit in practice, with the write_zero feature.

If a write zeros fork finishes quickly before wait_for_zero_forks()
gets called, then the SIGCHLD will be delivered before the signalfd
is setup.

While this is only theoretical, fix this by blocking the SIGCHLD
signal before forking any children.

Signed-off-by: Logan Gunthorpe <[e-mail]>
---
 Create.c | 1 +
 1 file changed, 1 insertion(+)

Patch

diff --git a/Create.c b/Create.c
index 4f992a22b7c9..bd4875e4a408 100644
--- a/Create.c
+++ b/Create.c
@@ -401,6 +401,7 @@  static int add_disks(int mdfd, struct mdinfo *info, struct shape *s,
 	 */
 	sigemptyset(&sigset);
 	sigaddset(&sigset, SIGINT);
+	sigaddset(&sigset, SIGCHLD);
 	sigprocmask(SIG_BLOCK, &sigset, &orig_sigset);
 	memset(zero_pids, 0, sizeof(zero_pids));