X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fstdio%2Ffreopen.c;h=6c1b575f527963566a7b457f29c18dea45b2505a;hb=6d861ac87491a207e4599c44b61d142f0a601c2d;hp=5b4f126dbddbcf4c9c11c5d177e48345e197be29;hpb=708c91f4e9be2cfd6d35e71361956e13f3201b85;p=musl

diff --git a/src/stdio/freopen.c b/src/stdio/freopen.c
index 5b4f126d..6c1b575f 100644
--- a/src/stdio/freopen.c
+++ b/src/stdio/freopen.c
@@ -1,39 +1,47 @@
 #include "stdio_impl.h"
+#include <fcntl.h>
 
 /* The basic idea of this implementation is to open a new FILE,
  * hack the necessary parts of the new FILE into the old one, then
  * close the new FILE. */
 
-/* Locking is not necessary because, in the event of failure, the stream
- * passed to freopen is invalid as soon as freopen is called. */
+/* Locking IS necessary because another thread may provably hold the
+ * lock, via flockfile or otherwise, when freopen is called, and in that
+ * case, freopen cannot act until the lock is released. */
+
+int __dup3(int, int, int);
 
 FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *restrict f)
 {
-	int fl;
+	int fl = __fmodeflags(mode);
 	FILE *f2;
 
+	FLOCK(f);
+
 	fflush(f);
 
 	if (!filename) {
-		f2 = fopen("/dev/null", mode);
-		if (!f2) goto fail;
-		fl = __syscall(SYS_fcntl, f2->fd, F_GETFL, 0);
+		if (fl&O_CLOEXEC)
+			__syscall(SYS_fcntl, f->fd, F_SETFD, FD_CLOEXEC);
+		fl &= ~(O_CREAT|O_EXCL|O_CLOEXEC);
 		if (syscall(SYS_fcntl, f->fd, F_SETFL, fl) < 0)
-			goto fail2;
+			goto fail;
 	} else {
 		f2 = fopen(filename, mode);
 		if (!f2) goto fail;
-		if (syscall(SYS_dup2, f2->fd, f->fd) < 0)
-			goto fail2;
-	}
+		if (f2->fd == f->fd) f2->fd = -1; /* avoid closing in fclose */
+		else if (__dup3(f2->fd, f->fd, fl&O_CLOEXEC)<0) goto fail2;
 
-	f->flags = (f->flags & F_PERM) | f2->flags;
-	f->read = f2->read;
-	f->write = f2->write;
-	f->seek = f2->seek;
-	f->close = f2->close;
+		f->flags = (f->flags & F_PERM) | f2->flags;
+		f->read = f2->read;
+		f->write = f2->write;
+		f->seek = f2->seek;
+		f->close = f2->close;
 
-	fclose(f2);
+		fclose(f2);
+	}
+
+	FUNLOCK(f);
 	return f;
 
 fail2: