Use mutex to protect access to librpm (#40525) (#40592)

More Librpm shenanigans. Turns out that it's possible for a user to run two instances of a metricset at once, which I didn't even know was possible or supported. However, librpm has some not-great threadsafety in it, and it's also possible for a shutdown operation to call dlclose while another thread is in the middle of accessing the SO. This adds a global mutex so we can't have multiple threads stepping on each other during RPM operations.

I tested this a bit, and I couldn't get it to crash while running multiple instances of the package metricset, but at this point librpm is so easy to break I would consider it more "best effort" than anything else.

(cherry picked from commit 46fd21c)

Co-authored-by: Alex K. <8418476+fearful-symmetry@users.noreply.github.com>

CHANGELOG.next.asciidoc

@@ -79,9 +79,9 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 
 *Auditbeat*
 
+- Fix segfaults that may happen if user runs multiple instances of the package metricset {pull}40525[40525]
 - Fix incorrect definition of struct utmp for arm64 {pull}40541[40541]
 
-
 *Filebeat*
 
 - [Gcs Input] - Added missing locks for safe concurrency {pull}34914[34914]

x-pack/auditbeat/module/system/package/rpm_linux.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"runtime"
 	"strings"
+	"sync"
 	"time"
 	"unsafe"
 
@@ -168,9 +169,12 @@ const (
 )
 
 var openedLibrpm *librpm
+var librpmLock sync.Mutex
 
 // closeDataset performs cleanup when the dataset is closed.
 func closeDataset() error {
+	librpmLock.Lock()
+	defer librpmLock.Unlock()
 	if openedLibrpm != nil {
 		err := openedLibrpm.close()
 		openedLibrpm = nil
@@ -325,6 +329,8 @@ func openLibrpm() (*librpm, error) {
 }
 
 func listRPMPackages() ([]*Package, error) {
+	librpmLock.Lock()
+	defer librpmLock.Unlock()
 	// In newer versions, librpm is using the thread-local variable
 	// `disableInterruptSafety` in rpmio/rpmsq.c to disable signal
 	// traps. To make sure our settings remain in effect throughout
@@ -376,7 +382,6 @@ func listRPMPackages() ([]*Package, error) {
 
 		packages = append(packages, pkg)
 	}
-
 	return packages, nil
 }