Issue #21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew.
diff --git a/Python/random.c b/Python/random.c
index cdace00..2941ba1 100644
--- a/Python/random.c
+++ b/Python/random.c
@@ -3,6 +3,9 @@
#include <windows.h>
#else
#include <fcntl.h>
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
#endif
#ifdef Py_DEBUG
@@ -69,7 +72,11 @@
#ifndef MS_WINDOWS
-static int urandom_fd = -1;
+static struct {
+ int fd;
+ dev_t st_dev;
+ ino_t st_ino;
+} urandom_cache = { -1 };
/* Read size bytes from /dev/urandom into buffer.
Call Py_FatalError() on error. */
@@ -109,12 +116,24 @@
{
int fd;
Py_ssize_t n;
+ struct stat st;
if (size <= 0)
return 0;
- if (urandom_fd >= 0)
- fd = urandom_fd;
+ if (urandom_cache.fd >= 0) {
+ /* Does the fd point to the same thing as before? (issue #21207) */
+ if (fstat(urandom_cache.fd, &st)
+ || st.st_dev != urandom_cache.st_dev
+ || st.st_ino != urandom_cache.st_ino) {
+ /* Something changed: forget the cached fd (but don't close it,
+ since it probably points to something important for some
+ third-party code). */
+ urandom_cache.fd = -1;
+ }
+ }
+ if (urandom_cache.fd >= 0)
+ fd = urandom_cache.fd;
else {
Py_BEGIN_ALLOW_THREADS
fd = _Py_open("/dev/urandom", O_RDONLY);
@@ -129,14 +148,24 @@
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
- if (urandom_fd >= 0) {
+ if (urandom_cache.fd >= 0) {
/* urandom_fd was initialized by another thread while we were
not holding the GIL, keep it. */
close(fd);
- fd = urandom_fd;
+ fd = urandom_cache.fd;
}
- else
- urandom_fd = fd;
+ else {
+ if (fstat(fd, &st)) {
+ PyErr_SetFromErrno(PyExc_OSError);
+ close(fd);
+ return -1;
+ }
+ else {
+ urandom_cache.fd = fd;
+ urandom_cache.st_dev = st.st_dev;
+ urandom_cache.st_ino = st.st_ino;
+ }
+ }
}
Py_BEGIN_ALLOW_THREADS
@@ -168,9 +197,9 @@
static void
dev_urandom_close(void)
{
- if (urandom_fd >= 0) {
- close(urandom_fd);
- urandom_fd = -1;
+ if (urandom_cache.fd >= 0) {
+ close(urandom_cache.fd);
+ urandom_cache.fd = -1;
}
}