From 7125a109dcc55628336ff3f58e59e503f4d7694d Mon Sep 17 00:00:00 2001
From: Chunwei Chen <david.chen@nutanix.com>
Date: Mon, 28 Oct 2019 09:49:44 -0700
Subject: [PATCH] Fix zpool history unbounded memory usage

In original implementation, zpool history will read the whole history
before printing anything, causing memory usage goes unbounded. We fix
this by breaking it into read-print iterations.

Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Closes #9516
---
 cmd/zpool/zpool_main.c   | 44 +++++++++++++++++++++++++---------------
 include/libzfs.h         |  3 ++-
 lib/libzfs/libzfs_pool.c | 20 ++++++++++--------
 3 files changed, 41 insertions(+), 26 deletions(-)

diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c
index 7a95add94a20..6071babfd027 100644
--- a/cmd/zpool/zpool_main.c
+++ b/cmd/zpool/zpool_main.c
@@ -8518,24 +8518,12 @@ typedef struct hist_cbdata {
 	boolean_t internal;
 } hist_cbdata_t;
 
-/*
- * Print out the command history for a specific pool.
- */
-static int
-get_history_one(zpool_handle_t *zhp, void *data)
+static void
+print_history_records(nvlist_t *nvhis, hist_cbdata_t *cb)
 {
-	nvlist_t *nvhis;
 	nvlist_t **records;
 	uint_t numrecords;
-	int ret, i;
-	hist_cbdata_t *cb = (hist_cbdata_t *)data;
-
-	cb->first = B_FALSE;
-
-	(void) printf(gettext("History for '%s':\n"), zpool_get_name(zhp));
-
-	if ((ret = zpool_get_history(zhp, &nvhis)) != 0)
-		return (ret);
+	int i;
 
 	verify(nvlist_lookup_nvlist_array(nvhis, ZPOOL_HIST_RECORD,
 	    &records, &numrecords) == 0);
@@ -8639,8 +8627,32 @@ get_history_one(zpool_handle_t *zhp, void *data)
 		(void) printf("]");
 		(void) printf("\n");
 	}
+}
+
+/*
+ * Print out the command history for a specific pool.
+ */
+static int
+get_history_one(zpool_handle_t *zhp, void *data)
+{
+	nvlist_t *nvhis;
+	int ret;
+	hist_cbdata_t *cb = (hist_cbdata_t *)data;
+	uint64_t off = 0;
+	boolean_t eof = B_FALSE;
+
+	cb->first = B_FALSE;
+
+	(void) printf(gettext("History for '%s':\n"), zpool_get_name(zhp));
+
+	while (!eof) {
+		if ((ret = zpool_get_history(zhp, &nvhis, &off, &eof)) != 0)
+			return (ret);
+
+		print_history_records(nvhis, cb);
+		nvlist_free(nvhis);
+	}
 	(void) printf("\n");
-	nvlist_free(nvhis);
 
 	return (ret);
 }
diff --git a/include/libzfs.h b/include/libzfs.h
index 7828a2759623..8e9f6fb3fc1b 100644
--- a/include/libzfs.h
+++ b/include/libzfs.h
@@ -432,7 +432,8 @@ typedef enum {
 extern char *zpool_vdev_name(libzfs_handle_t *, zpool_handle_t *, nvlist_t *,
     int name_flags);
 extern int zpool_upgrade(zpool_handle_t *, uint64_t);
-extern int zpool_get_history(zpool_handle_t *, nvlist_t **);
+extern int zpool_get_history(zpool_handle_t *, nvlist_t **, uint64_t *,
+    boolean_t *);
 extern int zpool_events_next(libzfs_handle_t *, nvlist_t **, int *, unsigned,
     int);
 extern int zpool_events_clear(libzfs_handle_t *, int *);
diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index 75ce7c9abad6..380229da5a88 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -4160,33 +4160,37 @@ get_history(zpool_handle_t *zhp, char *buf, uint64_t *off, uint64_t *len)
  * Retrieve the command history of a pool.
  */
 int
-zpool_get_history(zpool_handle_t *zhp, nvlist_t **nvhisp)
+zpool_get_history(zpool_handle_t *zhp, nvlist_t **nvhisp, uint64_t *off,
+    boolean_t *eof)
 {
 	char *buf;
 	int buflen = 128 * 1024;
-	uint64_t off = 0;
 	nvlist_t **records = NULL;
 	uint_t numrecords = 0;
 	int err, i;
+	uint64_t start = *off;
 
 	buf = malloc(buflen);
 	if (buf == NULL)
 		return (ENOMEM);
-	do {
+	/* process about 1MB a time */
+	while (*off - start < 1024 * 1024) {
 		uint64_t bytes_read = buflen;
 		uint64_t leftover;
 
-		if ((err = get_history(zhp, buf, &off, &bytes_read)) != 0)
+		if ((err = get_history(zhp, buf, off, &bytes_read)) != 0)
 			break;
 
 		/* if nothing else was read in, we're at EOF, just return */
-		if (!bytes_read)
+		if (!bytes_read) {
+			*eof = B_TRUE;
 			break;
+		}
 
 		if ((err = zpool_history_unpack(buf, bytes_read,
 		    &leftover, &records, &numrecords)) != 0)
 			break;
-		off -= leftover;
+		*off -= leftover;
 		if (leftover == bytes_read) {
 			/*
 			 * no progress made, because buffer is not big enough
@@ -4198,9 +4202,7 @@ zpool_get_history(zpool_handle_t *zhp, nvlist_t **nvhisp)
 			if (buf == NULL)
 				return (ENOMEM);
 		}
-
-		/* CONSTCOND */
-	} while (1);
+	}
 
 	free(buf);