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gh-116008: Detect freed thread state in faulthandler (#141988)

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Add _PyMem_IsULongFreed() function.
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Victor Stinner 2025-11-27 12:35:00 +01:00 • committed by GitHub
parent 83d8134c5b
commit d5d9e89dde
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2 changed files with 40 additions and 4 deletions
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21
Include/internal/pycore_pymem.h
View file

@ -70,6 +70,27 @@ static inline int _PyMem_IsPtrFreed(const void *ptr)
#endif
}
// Similar to _PyMem_IsPtrFreed() but expects an 'unsigned long' instead of a
// pointer.
static inline int _PyMem_IsULongFreed(unsigned long value)
{
#if SIZEOF_LONG == 8
return (value == 0
|| value == (unsigned long)0xCDCDCDCDCDCDCDCD
|| value == (unsigned long)0xDDDDDDDDDDDDDDDD
|| value == (unsigned long)0xFDFDFDFDFDFDFDFD
|| value == (unsigned long)0xFFFFFFFFFFFFFFFF);
#elif SIZEOF_LONG == 4
return (value == 0
|| value == (unsigned long)0xCDCDCDCD
|| value == (unsigned long)0xDDDDDDDD
|| value == (unsigned long)0xFDFDFDFD
|| value == (unsigned long)0xFFFFFFFF);
#else
# error "unknown long size"
#endif
}
extern int _PyMem_GetAllocatorName(
const char *name,
PyMemAllocatorName *allocator);

23
Python/traceback.c
View file

@ -1094,6 +1094,9 @@ tstate_is_freed(PyThreadState *tstate)
if (_PyMem_IsPtrFreed(tstate->interp)) {
return 1;
}
if (_PyMem_IsULongFreed(tstate->thread_id)) {
return 1;
}
return 0;
}
@ -1113,7 +1116,7 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
}
if (tstate_is_freed(tstate)) {
PUTS(fd, " <tstate is freed>\n");
PUTS(fd, " <freed thread state>\n");
return;
}
@ -1138,12 +1141,16 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
PUTS(fd, " <freed frame>\n");
break;
}
// Read frame->previous early since memory can be freed during
// dump_frame()
_PyInterpreterFrame *previous = frame->previous;
if (dump_frame(fd, frame) < 0) {
PUTS(fd, " <invalid frame>\n");
break;
}
frame = frame->previous;
frame = previous;
if (frame == NULL) {
break;
}
@ -1240,7 +1247,9 @@ write_thread_id(int fd, PyThreadState *tstate, int is_current)
tstate->thread_id,
sizeof(unsigned long) * 2);
write_thread_name(fd, tstate);
if (!_PyMem_IsULongFreed(tstate->thread_id)) {
write_thread_name(fd, tstate);
}
PUTS(fd, " (most recent call first):\n");
}
@ -1298,7 +1307,6 @@ _Py_DumpTracebackThreads(int fd, PyInterpreterState *interp,
return "unable to get the thread head state";
/* Dump the traceback of each thread */
tstate = PyInterpreterState_ThreadHead(interp);
unsigned int nthreads = 0;
_Py_BEGIN_SUPPRESS_IPH
do
@ -1309,11 +1317,18 @@ _Py_DumpTracebackThreads(int fd, PyInterpreterState *interp,
PUTS(fd, "...\n");
break;
}
if (tstate_is_freed(tstate)) {
PUTS(fd, "<freed thread state>\n");
break;
}
write_thread_id(fd, tstate, tstate == current_tstate);
if (tstate == current_tstate && tstate->interp->gc.collecting) {
PUTS(fd, " Garbage-collecting\n");
}
dump_traceback(fd, tstate, 0);
tstate = PyThreadState_Next(tstate);
nthreads++;
} while (tstate != NULL);