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Avoid kernel panic when attaching a process which may not be stopped

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by debugger, e.g process is dumping core. Only access p_xthread if
P_STOPPED_TRACE is set, this means thread is ready to exchange signal
with debugger, print a warning if P_STOPPED_TRACE is not set due to
some bugs in other code, if there is.

The patch has been tested by Anish Mistry mistry.7 at osu dot edu, and
is slightly adjusted.
This commit is contained in:
David Xu 2005-12-24 02:59:29 +00:00
parent 8abb0189ca
commit d7bc12b096
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=153697
2 changed files with 30 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sys/kern/kern_sig.c
View File

@ -2272,7 +2272,6 @@ do_tdsignal(struct proc *p, struct thread *td, int sig, ksiginfo_t *ksi)
goto out;
p->p_flag |= P_STOPPED_SIG;
p->p_xstat = sig;
p->p_xthread = td;
mtx_lock_spin(&sched_lock);
FOREACH_THREAD_IN_PROC(p, td0) {
if (TD_IS_SLEEPING(td0) &&
@ -2599,7 +2598,6 @@ issignal(td)
&p->p_mtx.mtx_object, "Catching SIGSTOP");
p->p_flag |= P_STOPPED_SIG;
p->p_xstat = sig;
p->p_xthread = td;
mtx_lock_spin(&sched_lock);
FOREACH_THREAD_IN_PROC(p, td0) {
if (TD_IS_SLEEPING(td0) &&

56
sys/kern/sys_process.c
View File

@ -491,7 +491,6 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
int error, write, tmp, num;
int proctree_locked = 0;
lwpid_t tid = 0, *buf;
pid_t saved_pid = pid;
#ifdef COMPAT_IA32
int wrap32 = 0, safe = 0;
struct ptrace_io_desc32 *piod32 = NULL;
@ -567,7 +566,12 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
}
if (tid == 0) {
td2 = FIRST_THREAD_IN_PROC(p);
if ((p->p_flag & P_STOPPED_TRACE) != 0) {
KASSERT(p->p_xthread != NULL, ("NULL p_xthread"));
td2 = p->p_xthread;
} else {
td2 = FIRST_THREAD_IN_PROC(p);
}
tid = td2->td_tid;
}
@ -637,12 +641,19 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
}
/* not currently stopped */
if (!P_SHOULDSTOP(p) || p->p_suspcount != p->p_numthreads ||
if ((p->p_flag & (P_STOPPED_SIG | P_STOPPED_TRACE)) == 0 ||
p->p_suspcount != p->p_numthreads ||
(p->p_flag & P_WAITED) == 0) {
error = EBUSY;
goto fail;
}
if ((p->p_flag & P_STOPPED_TRACE) == 0) {
static int count = 0;
if (count++ == 0)
printf("P_STOPPED_TRACE not set.\n");
}
/* OK */
break;
}
@ -795,17 +806,14 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
if (proctree_locked)
sx_xunlock(&proctree_lock);
/* deliver or queue signal */
if (P_SHOULDSTOP(p)) {
p->p_xstat = data;
mtx_lock_spin(&sched_lock);
td2->td_flags &= ~TDF_XSIG;
mtx_unlock_spin(&sched_lock);
td2->td_xsig = data;
p->p_xstat = data;
p->p_xthread = NULL;
if ((p->p_flag & (P_STOPPED_SIG | P_STOPPED_TRACE)) != 0) {
mtx_lock_spin(&sched_lock);
if (saved_pid <= PID_MAX) {
p->p_xthread->td_flags &= ~TDF_XSIG;
p->p_xthread->td_xsig = data;
} else {
td2->td_flags &= ~TDF_XSIG;
td2->td_xsig = data;
}
p->p_xthread = NULL;
if (req == PT_DETACH) {
struct thread *td3;
FOREACH_THREAD_IN_PROC(p, td3)
@ -818,15 +826,16 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
*/
mtx_unlock_spin(&sched_lock);
thread_continued(p);
p->p_flag &= ~(P_STOPPED_TRACE|P_STOPPED_SIG);
p->p_flag &= ~(P_STOPPED_TRACE|P_STOPPED_SIG|P_WAITED);
mtx_lock_spin(&sched_lock);
thread_unsuspend(p);
mtx_unlock_spin(&sched_lock);
} else if (data) {
psignal(p, data);
}
PROC_UNLOCK(p);
if (data)
psignal(p, data);
PROC_UNLOCK(p);
return (0);
case PT_WRITE_I:
@ -964,16 +973,11 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
return (EINVAL);
pl = addr;
_PHOLD(p);
if (saved_pid <= PID_MAX) {
pl->pl_lwpid = p->p_xthread->td_tid;
pl->pl_lwpid = td2->td_tid;
if (td2->td_flags & TDF_XSIG)
pl->pl_event = PL_EVENT_SIGNAL;
} else {
pl->pl_lwpid = td2->td_tid;
if (td2->td_flags & TDF_XSIG)
pl->pl_event = PL_EVENT_SIGNAL;
else
pl->pl_event = 0;
}
else
pl->pl_event = 0;
if (td2->td_pflags & TDP_SA) {
pl->pl_flags = PL_FLAG_SA;
if (td2->td_upcall && !TD_CAN_UNBIND(td2))