114 lines
3.7 KiB
Diff
114 lines
3.7 KiB
Diff
# HG changeset patch
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# User martin
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# Date 1494116427 -3600
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# Sun May 07 01:20:27 2017 +0100
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# Node ID 0bd3170be8c729dfaa88e7aa97449b2f36c650a9
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# Parent baf64c88538f477d7f5a0cf90b670108ac312375
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8043780, PR3368: Use open(O_CLOEXEC) instead of fcntl(FD_CLOEXEC)
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Summary: Use open(O_CLOEXEC) where available; fall back to FD_CLOEXEC when necessary
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Reviewed-by: rasbold, dholmes
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diff --git a/src/os/linux/vm/os_linux.cpp b/src/os/linux/vm/os_linux.cpp
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--- openjdk/hotspot/src/os/linux/vm/os_linux.cpp
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+++ openjdk/hotspot/src/os/linux/vm/os_linux.cpp
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@@ -5282,38 +5282,16 @@
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errno = ENAMETOOLONG;
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return -1;
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}
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- int fd;
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int o_delete = (oflag & O_DELETE);
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oflag = oflag & ~O_DELETE;
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- fd = ::open64(path, oflag, mode);
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- if (fd == -1) return -1;
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-
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- //If the open succeeded, the file might still be a directory
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- {
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- struct stat64 buf64;
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- int ret = ::fstat64(fd, &buf64);
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- int st_mode = buf64.st_mode;
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-
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- if (ret != -1) {
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- if ((st_mode & S_IFMT) == S_IFDIR) {
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- errno = EISDIR;
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- ::close(fd);
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- return -1;
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- }
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- } else {
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- ::close(fd);
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- return -1;
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- }
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- }
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-
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- /*
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- * All file descriptors that are opened in the JVM and not
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- * specifically destined for a subprocess should have the
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- * close-on-exec flag set. If we don't set it, then careless 3rd
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- * party native code might fork and exec without closing all
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- * appropriate file descriptors (e.g. as we do in closeDescriptors in
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- * UNIXProcess.c), and this in turn might:
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+
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+ /* All file descriptors that are opened in the Java process and not
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+ * specifically destined for a subprocess should have the close-on-exec
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+ * flag set. If we don't set it, then careless 3rd party native code
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+ * might fork and exec without closing all appropriate file descriptors
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+ * (e.g. as we do in closeDescriptors in UNIXProcess.c), and this in
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+ * turn might:
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*
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* - cause end-of-file to fail to be detected on some file
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* descriptors, resulting in mysterious hangs, or
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@@ -5329,12 +5307,49 @@
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* 4843136: (process) pipe file descriptor from Runtime.exec not being closed
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* 6339493: (process) Runtime.exec does not close all file descriptors on Solaris 9
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*/
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+ // Modern Linux kernels (after 2.6.23 2007) support O_CLOEXEC with open().
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+ // O_CLOEXEC is preferable to using FD_CLOEXEC on an open file descriptor
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+ // because it saves a system call and removes a small window where the flag
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+ // is unset. On ancient Linux kernels the O_CLOEXEC flag will be ignored
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+ // and we fall back to using FD_CLOEXEC (see below).
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+#ifdef O_CLOEXEC
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+ oflag |= O_CLOEXEC;
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+#endif
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+
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+ int fd = ::open64(path, oflag, mode);
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+ if (fd == -1) return -1;
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+
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+ //If the open succeeded, the file might still be a directory
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+ {
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+ struct stat64 buf64;
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+ int ret = ::fstat64(fd, &buf64);
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+ int st_mode = buf64.st_mode;
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+
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+ if (ret != -1) {
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+ if ((st_mode & S_IFMT) == S_IFDIR) {
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+ errno = EISDIR;
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+ ::close(fd);
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+ return -1;
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+ }
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+ } else {
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+ ::close(fd);
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+ return -1;
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+ }
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+ }
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+
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#ifdef FD_CLOEXEC
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- {
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- int flags = ::fcntl(fd, F_GETFD);
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- if (flags != -1)
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- ::fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
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+ // Validate that the use of the O_CLOEXEC flag on open above worked.
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+ // With recent kernels, we will perform this check exactly once.
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+ static sig_atomic_t O_CLOEXEC_is_known_to_work = 0;
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+ if (!O_CLOEXEC_is_known_to_work) {
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+ int flags = ::fcntl(fd, F_GETFD);
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+ if (flags != -1) {
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+ if ((flags & FD_CLOEXEC) != 0)
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+ O_CLOEXEC_is_known_to_work = 1;
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+ else
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+ ::fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
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}
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+ }
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#endif
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if (o_delete != 0) {
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