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exec: Cease tracing if credentials will change with the new image.

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This also prevents tracing to a P_INEXEC process since it could race
with other processes attaching to it in filemon_event_process_exec() due
to the filemon_get_proc() race of incrementing ref and then locking the
filemon.  With the no-P_INEXEC invariant in place the p_filemon may only
be the same or NULL when trying to drop it in
filemon_event_process_exec().

MFC after:	2 weeks
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D6545
This commit is contained in:
Bryan Drewery 2016-05-27 23:57:43 +00:00
parent 91970834ed
commit f14fbe72ec
2 changed files with 29 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
sys/dev/filemon/filemon.c
View file

@ -89,6 +89,7 @@ MALLOC_DEFINE(M_FILEMON, "filemon", "File access monitor");
struct filemon {
struct sx lock; /* Lock for this filemon. */
struct file *fp; /* Output file pointer. */
struct ucred *cred; /* Credential of tracer. */
char fname1[MAXPATHLEN]; /* Temporary filename buffer. */
char fname2[MAXPATHLEN]; /* Temporary filename buffer. */
char msgbufr[1024]; /* Output message buffer. */
@ -125,6 +126,8 @@ filemon_release(struct filemon *filemon)
*/
sx_assert(&filemon->lock, SA_UNLOCKED);
if (filemon->cred != NULL)
crfree(filemon->cred);
sx_destroy(&filemon->lock);
free(filemon, M_FILEMON);
}
@ -308,6 +311,9 @@ filemon_attach_proc(struct filemon *filemon, struct proc *p)
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);
@ -385,8 +391,8 @@ filemon_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag __unused,
/* Invalidate any existing processes already set. */
filemon_untrack_processes(filemon);
error = pget(*((pid_t *)data), PGET_CANDEBUG | PGET_NOTWEXIT,
&p);
error = pget(*((pid_t *)data),
PGET_CANDEBUG | PGET_NOTWEXIT | PGET_NOTINEXEC, &p);
if (error == 0) {
KASSERT(p->p_filemon != filemon,
("%s: proc %p didn't untrack filemon %p",
@ -407,7 +413,7 @@ 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;
@ -416,6 +422,7 @@ filemon_open(struct cdev *dev, int oflags __unused, int devtype __unused,
M_WAITOK | M_ZERO);
sx_init(&filemon->lock, "filemon");
refcount_init(&filemon->refcnt, 1);
filemon->cred = crhold(td->td_ucred);
error = devfs_set_cdevpriv(filemon, filemon_dtr);
if (error != 0)

19
sys/dev/filemon/filemon_wrapper.c
View file

@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
#include <sys/eventhandler.h>
#include <sys/filedesc.h>
#include <sys/imgact.h>
#include <sys/priv.h>
#include <sys/sx.h>
#include <sys/vnode.h>
@ -112,6 +113,24 @@ filemon_event_process_exec(void *arg __unused, struct proc *p,
filemon_output(filemon, filemon->msgbufr, len);
/* If the credentials changed then cease tracing. */
if (imgp->newcred != NULL &&
imgp->credential_setid &&
priv_check_cred(filemon->cred,
PRIV_DEBUG_DIFFCRED, 0) != 0) {
/*
* It may have changed to NULL already, but
* will not be re-attached by anything else.
*/
if (p->p_filemon != NULL) {
KASSERT(p->p_filemon == filemon,
("%s: proc %p didn't have expected"
" filemon %p", __func__, p, filemon));
filemon_proc_drop(p);
}
}
filemon_drop(filemon);
}
}