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[RFC,v2,5/7] Add helpers to read/write to a file through the chrooted thread

Message ID 20190521124701.61849-6-trond.myklebust@hammerspace.com (mailing list archive)
State New, archived
Headers show
Series Add a root_dir option to nfs.conf | expand

Commit Message

Trond Myklebust May 21, 2019, 12:46 p.m. UTC 
Add helper functions to do synchronous I/O to a file from inside the
chrooted environment. This ensures that calls to kern_path() in the
kernel resolves to paths that are relative to the nfsd root directory.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 support/include/workqueue.h |  4 ++
 support/misc/workqueue.c    | 78 +++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)
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Patch

diff --git a/support/include/workqueue.h b/support/include/workqueue.h
index 518be82f1b34..21b1ee6bc873 100644
--- a/support/include/workqueue.h
+++ b/support/include/workqueue.h
@@ -15,4 +15,8 @@  void xthread_work_run_sync(struct xthread_workqueue *wq,
 void xthread_workqueue_chroot(struct xthread_workqueue *wq,
 		const char *path);
 
+ssize_t xthread_read(struct xthread_workqueue *wq,
+		int fd, char *buf, size_t len);
+ssize_t xthread_write(struct xthread_workqueue *wq,
+		int fd, const char *buf, size_t len);
 #endif
diff --git a/support/misc/workqueue.c b/support/misc/workqueue.c
index b8d03446f2c7..9d967cef6547 100644
--- a/support/misc/workqueue.c
+++ b/support/misc/workqueue.c
@@ -1,3 +1,4 @@ 
+#include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>
 
@@ -197,6 +198,72 @@  void xthread_workqueue_chroot(struct xthread_workqueue *wq,
 	xthread_work_run_sync(wq, xthread_workqueue_do_chroot, (void *)path);
 }
 
+struct xthread_read_data {
+	int fd;
+	char *buf;
+	size_t len;
+	ssize_t ret;
+	int err;
+};
+
+static void xthread_readfunc(void *data)
+{
+	struct xthread_read_data *d = data;
+
+	d->ret = read(d->fd, d->buf, d->len);
+	if (d->ret < 0)
+		d->err = errno;
+}
+
+ssize_t xthread_read(struct xthread_workqueue *wq,
+		int fd, char *buf, size_t len)
+{
+	struct xthread_read_data data = {
+		fd,
+		buf,
+		len,
+		0,
+		0
+	};
+	xthread_work_run_sync(wq, xthread_readfunc, &data);
+	if (data.ret < 0)
+		errno = data.err;
+	return data.ret;
+}
+
+struct xthread_write_data {
+	int fd;
+	const char *buf;
+	size_t len;
+	ssize_t ret;
+	int err;
+};
+
+static void xthread_writefunc(void *data)
+{
+	struct xthread_write_data *d = data;
+
+	d->ret = write(d->fd, d->buf, d->len);
+	if (d->ret < 0)
+		d->err = errno;
+}
+
+ssize_t xthread_write(struct xthread_workqueue *wq,
+		int fd, const char *buf, size_t len)
+{
+	struct xthread_write_data data = {
+		fd,
+		buf,
+		len,
+		0,
+		0
+	};
+	xthread_work_run_sync(wq, xthread_writefunc, &data);
+	if (data.ret < 0)
+		errno = data.err;
+	return data.ret;
+}
+
 #else
 
 struct xthread_workqueue {
@@ -225,4 +292,15 @@  void xthread_workqueue_chroot(struct xthread_workqueue *wq,
 	xlog_err("Unable to run as chroot");
 }
 
+ssize_t xthread_read(struct xthread_workqueue *wq,
+		int fd, char *buf, size_t len)
+{
+	return read(fd, buf, len);
+}
+
+ssize_t xthread_write(struct xthread_workqueue *wq,
+		int fd, const char *buf, size_t len)
+{
+	return write(fd, buf, len);
+}
 #endif /* defined(HAVE_SCHED_H) && defined(HAVE_LIBPTHREAD) && defined(HAVE_UNSHARE) */