Author: avg
Date: Tue Dec 3 09:48:43 2019
New Revision: 355325
URL: https://svnweb.freebsd.org/changeset/base/355325
Log:
devstat_selectdevs: resize dev_select only after copying data out of it
The resizing could be a downsizing so some data would be lost and we
could attempt to read past the end of the new memory allocation.
MFC after: 2 weeks
Sponsored by: Panzura
Modified:
head/lib/libdevstat/devstat.c
Modified: head/lib/libdevstat/devstat.c
==============================================================================
--- head/lib/libdevstat/devstat.c Tue Dec 3 09:12:53 2019
(r355324)
+++ head/lib/libdevstat/devstat.c Tue Dec 3 09:48:43 2019
(r355325)
@@ -584,10 +584,10 @@ devstat_selectdevs(struct device_selection **dev_selec
* In this case, we have selected devices before, but the device
* list has changed since we last selected devices, so we need to
* either enlarge or reduce the size of the device selection list.
+ * But delay the resizing until after copying the data to old_dev_select
+ * as to not lose any data in the case of reducing the size.
*/
} else if (*num_selections != numdevs) {
- *dev_select = (struct device_selection *)reallocf(*dev_select,
- numdevs * sizeof(struct device_selection));
*select_generation = current_generation;
init_selections = 1;
/*
@@ -643,6 +643,11 @@ devstat_selectdevs(struct device_selection **dev_selec
old_num_selections = *num_selections;
bcopy(*dev_select, old_dev_select,
sizeof(struct device_selection) * *num_selections);
+ }
+
+ if (!changed && *num_selections != numdevs) {
+ *dev_select = (struct device_selection *)reallocf(*dev_select,
+ numdevs * sizeof(struct device_selection));
}
if (init_selections != 0) {
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