1 files changed, 283 insertions, 98 deletions

diff --git a/sys/dev/filemon/filemon.c b/sys/dev/filemon/filemon.c
index cd40c5a..919af9d 100644
--- a/sys/dev/filemon/filemon.c
+++ b/sys/dev/filemon/filemon.c
@@ -1,7 +1,7 @@
 /*-
  * Copyright (c) 2011, David E. O'Brien.
  * Copyright (c) 2009-2011, Juniper Networks, Inc.
- * Copyright (c) 2015, EMC Corp.
+ * Copyright (c) 2015-2016, EMC Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -46,7 +46,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/poll.h>
 #include <sys/proc.h>
-#include <sys/queue.h>
 #include <sys/sx.h>
 #include <sys/syscall.h>
 #include <sys/sysent.h>
@@ -55,16 +54,12 @@ __FBSDID("$FreeBSD$");
 
 #include "filemon.h"
 
-#if defined(COMPAT_IA32) || defined(COMPAT_FREEBSD32) || defined(COMPAT_ARCH32)
+#if defined(COMPAT_FREEBSD32)
 #include <compat/freebsd32/freebsd32_syscall.h>
 #include <compat/freebsd32/freebsd32_proto.h>
-
-extern struct sysentvec ia32_freebsd_sysvec;
+#include <compat/freebsd32/freebsd32_util.h>
 #endif
 
-extern struct sysentvec elf32_freebsd_sysvec;
-extern struct sysentvec elf64_freebsd_sysvec;
-
 static d_close_t	filemon_close;
 static d_ioctl_t	filemon_ioctl;
 static d_open_t		filemon_open;
@@ -80,27 +75,119 @@ static struct cdevsw filemon_cdevsw = {
 MALLOC_DECLARE(M_FILEMON);
 MALLOC_DEFINE(M_FILEMON, "filemon", "File access monitor");
 
+/*
+ * The filemon->lock protects several things currently:
+ * - fname1/fname2/msgbufr are pre-allocated and used per syscall
+ *   for logging and copyins rather than stack variables.
+ * - Serializing the filemon's log output.
+ * - Preventing inheritance or removal of the filemon into proc.p_filemon.
+ */
 struct filemon {
-	TAILQ_ENTRY(filemon) link;	/* Link into the in-use list. */
-	struct sx	lock;		/* Lock mutex for this filemon. */
+	struct sx	lock;		/* Lock for this filemon. */
 	struct file	*fp;		/* Output file pointer. */
-	struct proc     *p;		/* The process being monitored. */
+	struct ucred	*cred;		/* Credential of tracer. */
 	char		fname1[MAXPATHLEN]; /* Temporary filename buffer. */
 	char		fname2[MAXPATHLEN]; /* Temporary filename buffer. */
 	char		msgbufr[1024];	/* Output message buffer. */
+	int		error;		/* Log write error, returned on close(2). */
+	u_int		refcnt;		/* Pointer reference count. */
+	u_int		proccnt;	/* Process count. */
 };
 
-static TAILQ_HEAD(, filemon) filemons_inuse = TAILQ_HEAD_INITIALIZER(filemons_inuse);
-static TAILQ_HEAD(, filemon) filemons_free = TAILQ_HEAD_INITIALIZER(filemons_free);
-static struct sx access_lock;
-
 static struct cdev *filemon_dev;
+static void filemon_output(struct filemon *filemon, char *msg, size_t len);
+
+static __inline struct filemon *
+filemon_acquire(struct filemon *filemon)
+{
+
+	if (filemon != NULL)
+		refcount_acquire(&filemon->refcnt);
+	return (filemon);
+}
+
+/*
+ * Release a reference and free on the last one.
+ */
+static void
+filemon_release(struct filemon *filemon)
+{
+
+	if (refcount_release(&filemon->refcnt) == 0)
+		return;
+	/*
+	 * There are valid cases of releasing while locked, such as in
+	 * filemon_untrack_processes, but none which are done where there
+	 * is not at least 1 reference remaining.
+	 */
+	sx_assert(&filemon->lock, SA_UNLOCKED);
+
+	if (filemon->cred != NULL)
+		crfree(filemon->cred);
+	sx_destroy(&filemon->lock);
+	free(filemon, M_FILEMON);
+}
+
+/*
+ * Acquire the proc's p_filemon reference and lock the filemon.
+ * The proc's p_filemon may not match this filemon on return.
+ */
+static struct filemon *
+filemon_proc_get(struct proc *p)
+{
+	struct filemon *filemon;
+
+	PROC_LOCK(p);
+	filemon = filemon_acquire(p->p_filemon);
+	PROC_UNLOCK(p);
+
+	if (filemon == NULL)
+		return (NULL);
+	/*
+	 * The p->p_filemon may have changed by now.  That case is handled
+	 * by the exit and fork hooks and filemon_attach_proc specially.
+	 */
+	sx_xlock(&filemon->lock);
+	return (filemon);
+}
+
+/* Remove and release the filemon on the given process. */
+static void
+filemon_proc_drop(struct proc *p)
+{
+	struct filemon *filemon;
+
+	KASSERT(p->p_filemon != NULL, ("%s: proc %p NULL p_filemon",
+	    __func__, p));
+	sx_assert(&p->p_filemon->lock, SA_XLOCKED);
+	PROC_LOCK(p);
+	filemon = p->p_filemon;
+	p->p_filemon = NULL;
+	--filemon->proccnt;
+	PROC_UNLOCK(p);
+	/*
+	 * This should not be the last reference yet.  filemon_release()
+	 * cannot be called with filemon locked, which the caller expects
+	 * will stay locked.
+	 */
+	KASSERT(filemon->refcnt > 1, ("%s: proc %p dropping filemon %p "
+	    "with last reference", __func__, p, filemon));
+	filemon_release(filemon);
+}
+
+/* Unlock and release the filemon. */
+static __inline void
+filemon_drop(struct filemon *filemon)
+{
+
+	sx_xunlock(&filemon->lock);
+	filemon_release(filemon);
+}
 
-#include "filemon_lock.c"
 #include "filemon_wrapper.c"
 
 static void
-filemon_comment(struct filemon *filemon)
+filemon_write_header(struct filemon *filemon)
 {
 	int len;
 	struct timeval now;
@@ -115,35 +202,154 @@ filemon_comment(struct filemon *filemon)
 	filemon_output(filemon, filemon->msgbufr, len);
 }
 
+/*
+ * Invalidate the passed filemon in all processes.
+ */
 static void
-filemon_dtr(void *data)
+filemon_untrack_processes(struct filemon *filemon)
 {
-	struct filemon *filemon = data;
+	struct proc *p;
 
-	if (filemon != NULL) {
-		struct file *fp;
+	sx_assert(&filemon->lock, SA_XLOCKED);
 
-		/* Follow same locking order as filemon_pid_check. */
-		filemon_lock_write();
-		sx_xlock(&filemon->lock);
+	/* Avoid allproc loop if there is no need. */
+	if (filemon->proccnt == 0)
+		return;
 
-		/* Remove from the in-use list. */
-		TAILQ_REMOVE(&filemons_inuse, filemon, link);
+	/*
+	 * Processes in this list won't go away while here since
+	 * filemon_event_process_exit() will lock on filemon->lock
+	 * which we hold.
+	 */
+	sx_slock(&allproc_lock);
+	FOREACH_PROC_IN_SYSTEM(p) {
+		/*
+		 * No PROC_LOCK is needed to compare here since it is
+		 * guaranteed to not change since we have its filemon
+		 * locked.  Everything that changes this p_filemon will
+		 * be locked on it.
+		 */
+		if (p->p_filemon == filemon)
+			filemon_proc_drop(p);
+	}
+	sx_sunlock(&allproc_lock);
+
+	/*
+	 * It's possible some references were acquired but will be
+	 * dropped shortly as they are restricted from being
+	 * inherited.  There is at least the reference in cdevpriv remaining.
+	 */
+	KASSERT(filemon->refcnt > 0, ("%s: filemon %p should have "
+	    "references still.", __func__, filemon));
+	KASSERT(filemon->proccnt == 0, ("%s: filemon %p should not have "
+	    "attached procs still.", __func__, filemon));
+}
 
-		fp = filemon->fp;
-		filemon->fp = NULL;
-		filemon->p = NULL;
+/*
+ * Close out the log.
+ */
+static void
+filemon_close_log(struct filemon *filemon)
+{
+	struct file *fp;
+	struct timeval now;
+	size_t len;
 
-		/* Add to the free list. */
-		TAILQ_INSERT_TAIL(&filemons_free, filemon, link);
+	sx_assert(&filemon->lock, SA_XLOCKED);
+	if (filemon->fp == NULL)
+		return;
 
-		/* Give up write access. */
-		sx_xunlock(&filemon->lock);
-		filemon_unlock_write();
+	getmicrotime(&now);
+
+	len = snprintf(filemon->msgbufr,
+	    sizeof(filemon->msgbufr),
+	    "# Stop %ju.%06ju\n# Bye bye\n",
+	    (uintmax_t)now.tv_sec, (uintmax_t)now.tv_usec);
+
+	filemon_output(filemon, filemon->msgbufr, len);
+	fp = filemon->fp;
+	filemon->fp = NULL;
+
+	sx_xunlock(&filemon->lock);
+	fdrop(fp, curthread);
+	sx_xlock(&filemon->lock);
+}
+
+/*
+ * The devfs file is being closed.  Untrace all processes.  It is possible
+ * filemon_close/close(2) was not called.
+ */
+static void
+filemon_dtr(void *data)
+{
+	struct filemon *filemon = data;
 
-		if (fp != NULL)
-			fdrop(fp, curthread);
+	if (filemon == NULL)
+		return;
+
+	sx_xlock(&filemon->lock);
+	/*
+	 * Detach the filemon.  It cannot be inherited after this.
+	 */
+	filemon_untrack_processes(filemon);
+	filemon_close_log(filemon);
+	filemon_drop(filemon);
+}
+
+/* Attach the filemon to the process. */
+static int
+filemon_attach_proc(struct filemon *filemon, struct proc *p)
+{
+	struct filemon *filemon2;
+
+	sx_assert(&filemon->lock, SA_XLOCKED);
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	KASSERT((p->p_flag & P_WEXIT) == 0,
+	    ("%s: filemon %p attaching to exiting process %p",
+	    __func__, filemon, p));
+	KASSERT((p->p_flag & P_INEXEC) == 0,
+	    ("%s: filemon %p attaching to execing process %p",
+	    __func__, filemon, p));
+
+	if (p->p_filemon == filemon)
+		return (0);
+	/*
+	 * Don't allow truncating other process traces.  It is
+	 * not really intended to trace procs other than curproc
+	 * anyhow.
+	 */
+	if (p->p_filemon != NULL && p != curproc)
+		return (EBUSY);
+	/*
+	 * Historic behavior of filemon has been to let a child initiate
+	 * tracing on itself and cease existing tracing.  Bmake
+	 * .META + .MAKE relies on this.  It is only relevant for attaching to
+	 * curproc.
+	 */
+	while (p->p_filemon != NULL) {
+		PROC_UNLOCK(p);
+		sx_xunlock(&filemon->lock);
+		while ((filemon2 = filemon_proc_get(p)) != NULL) {
+			/* It may have changed. */
+			if (p->p_filemon == filemon2)
+				filemon_proc_drop(p);
+			filemon_drop(filemon2);
+		}
+		sx_xlock(&filemon->lock);
+		PROC_LOCK(p);
+		/*
+		 * It may have been attached to, though unlikely.
+		 * Try again if needed.
+		 */
 	}
+
+	KASSERT(p->p_filemon == NULL,
+	    ("%s: proc %p didn't detach filemon %p", __func__, p,
+	    p->p_filemon));
+	p->p_filemon = filemon_acquire(filemon);
+	++filemon->proccnt;
+
+	return (0);
 }
 
 static int
@@ -173,15 +379,21 @@ filemon_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag __unused,
 		    &filemon->fp);
 		if (error == 0)
 			/* Write the file header. */
-			filemon_comment(filemon);
+			filemon_write_header(filemon);
 		break;
 
 	/* Set the monitored process ID. */
 	case FILEMON_SET_PID:
-		error = pget(*((pid_t *)data), PGET_CANDEBUG | PGET_NOTWEXIT,
-		    &p);
+		/* Invalidate any existing processes already set. */
+		filemon_untrack_processes(filemon);
+
+		error = pget(*((pid_t *)data),
+		    PGET_CANDEBUG | PGET_NOTWEXIT | PGET_NOTINEXEC, &p);
 		if (error == 0) {
-			filemon->p = p;
+			KASSERT(p->p_filemon != filemon,
+			    ("%s: proc %p didn't untrack filemon %p",
+			    __func__, p, filemon));
+			error = filemon_attach_proc(filemon, p);
 			PROC_UNLOCK(p);
 		}
 		break;
@@ -197,51 +409,51 @@ filemon_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag __unused,
 
 static int
 filemon_open(struct cdev *dev, int oflags __unused, int devtype __unused,
-    struct thread *td __unused)
+    struct thread *td)
 {
+	int error;
 	struct filemon *filemon;
 
-	/* Get exclusive write access. */
-	filemon_lock_write();
-
-	if ((filemon = TAILQ_FIRST(&filemons_free)) != NULL)
-		TAILQ_REMOVE(&filemons_free, filemon, link);
-
-	/* Give up write access. */
-	filemon_unlock_write();
-
-	if (filemon == NULL) {
-		filemon = malloc(sizeof(struct filemon), M_FILEMON,
-		    M_WAITOK | M_ZERO);
-		sx_init(&filemon->lock, "filemon");
-	}
-
-	devfs_set_cdevpriv(filemon, filemon_dtr);
-
-	/* Get exclusive write access. */
-	filemon_lock_write();
-
-	/* Add to the in-use list. */
-	TAILQ_INSERT_TAIL(&filemons_inuse, filemon, link);
+	filemon = malloc(sizeof(*filemon), M_FILEMON,
+	    M_WAITOK | M_ZERO);
+	sx_init(&filemon->lock, "filemon");
+	refcount_init(&filemon->refcnt, 1);
+	filemon->cred = crhold(td->td_ucred);
 
-	/* Give up write access. */
-	filemon_unlock_write();
+	error = devfs_set_cdevpriv(filemon, filemon_dtr);
+	if (error != 0)
+		filemon_release(filemon);
 
-	return (0);
+	return (error);
 }
 
+/* Called on close of last devfs file handle, before filemon_dtr(). */
 static int
 filemon_close(struct cdev *dev __unused, int flag __unused, int fmt __unused,
     struct thread *td __unused)
 {
+	struct filemon *filemon;
+	int error;
 
-	return (0);
+	if ((error = devfs_get_cdevpriv((void **) &filemon)) != 0)
+		return (error);
+
+	sx_xlock(&filemon->lock);
+	filemon_close_log(filemon);
+	error = filemon->error;
+	sx_xunlock(&filemon->lock);
+	/*
+	 * Processes are still being traced but won't log anything
+	 * now.  After this call returns filemon_dtr() is called which
+	 * will detach processes.
+	 */
+
+	return (error);
 }
 
 static void
 filemon_load(void *dummy __unused)
 {
-	sx_init(&access_lock, "filemons_inuse");
 
 	/* Install the syscall wrappers. */
 	filemon_wrapper_install();
@@ -253,38 +465,11 @@ filemon_load(void *dummy __unused)
 static int
 filemon_unload(void)
 {
- 	struct filemon *filemon;
-	int error = 0;
-
-	/* Get exclusive write access. */
-	filemon_lock_write();
-
-	if (TAILQ_FIRST(&filemons_inuse) != NULL)
-		error = EBUSY;
-	else {
-		destroy_dev(filemon_dev);
-
-		/* Deinstall the syscall wrappers. */
-		filemon_wrapper_deinstall();
-	}
 
-	/* Give up write access. */
-	filemon_unlock_write();
+	destroy_dev(filemon_dev);
+	filemon_wrapper_deinstall();
 
-	if (error == 0) {
-		/* free() filemon structs free list. */
-		filemon_lock_write();
-		while ((filemon = TAILQ_FIRST(&filemons_free)) != NULL) {
-			TAILQ_REMOVE(&filemons_free, filemon, link);
-			sx_destroy(&filemon->lock);
-			free(filemon, M_FILEMON);
-		}
-		filemon_unlock_write();
-
-		sx_destroy(&access_lock);
-	}
-
-	return (error);
+	return (0);
 }
 
 static int