test: fix race conditions in /dev/kmsg tests

The e2e tests for device access involving /dev/kmsg could fail
intermittently.  This was due to a race condition where concurrent
writes to the kernel log buffer by other processes, while the test
was reading from /dev/kmsg, could cause the read to fail with ESPIPE.

Fixes: #23882

Signed-off-by: Giuseppe Scrivano <[email protected]>

Author: giuseppe

test/e2e/run_device_test.go

@@ -50,7 +50,10 @@ var _ = Describe("Podman run device", func() {
 		Expect(session).Should(ExitCleanly())
 		if !isRootless() {
 			// Kernel 6.9.0 (2024-03) requires SYSLOG
-			session = podmanTest.Podman([]string{"run", "-q", "--security-opt", "label=disable", "--device", "/dev/kmsg", "--cap-add", "SYS_ADMIN,SYSLOG", ALPINE, "head", "-n", "1", "/dev/kmsg"})
+			// Do not read any data from the device (thus the -n 0), because there is a rare race condition that happens
+			// when another writes to the ring buffer when the device is already opened and that causes the following test
+			// to fail: https://github.com/containers/podman/issues/23882.
+			session = podmanTest.Podman([]string{"run", "-q", "--security-opt", "label=disable", "--device", "/dev/kmsg", "--cap-add", "SYS_ADMIN,SYSLOG", ALPINE, "head", "-n", "0", "/dev/kmsg"})
 			session.WaitWithDefaultTimeout()
 			Expect(session).Should(ExitCleanly())
 		}
@@ -152,9 +155,12 @@ var _ = Describe("Podman run device", func() {
 	})
 
 	It("podman run cannot access non default devices", func() {
-		session := podmanTest.Podman([]string{"run", "-v /dev:/dev-host", ALPINE, "head", "-1", "/dev-host/kmsg"})
+		// Unlikely to happen but do not read any data from the device (thus the -n 0), because there is a rare
+		// race condition that happens so the test would fail for the rare race condition instead of a failure
+		// reported by open(). More details: https://github.com/containers/podman/issues/23882.
+		session := podmanTest.Podman([]string{"run", "-v", "/dev:/dev-host", ALPINE, "head", "-n0", "/dev-host/kmsg"})
 		session.WaitWithDefaultTimeout()
-		Expect(session).Should(Not(ExitCleanly()))
+		Expect(session).To(ExitWithErrorRegex(1, "head: /dev-host/kmsg: (Operation not permitted|Permission denied)"))
 	})
 
 })