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libdm: fix stats walk compatibility with older dmsetup

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The current dmsetup.c handles DR_STATS and DR_STATS_META reports
separately in _display_info_cols(), meaning that the stats walk
functions are never called for these report types.

Versions before v2.02.159 have a loop using dm_stats_walk_do() and
dm_stats_walk_while(), that executes once for non-stats reports,
and once per region, or area, for DR_STATS/DR_STATS_META reports.

This older behaviour relies on the documented behaviour that the
walk functions will accept a NULL pointer as the struct dm_stats*
argument.

This was broken by commit f1f2df7b: the NULL test on dms and
dms->regions were incorrectly moved from the dm_stats_walk_end()
wrapper to the internal '_stats_walk_end()' helper.

Since the pointer is dereferenced in between these points, using
an older dmsetup with current libdm results in a segfault when
running a non-stats report:

  # dmsetup info -c vg00/lvol0
  Segmentation fault (core dumped)

Restore the NULL checks to the wrapper function as intended.
This commit is contained in:
Bryn M. Reeves 2016-09-27 14:35:22 +01:00
parent 0a480c5c52
commit 6ec8854fdb
2 changed files with 4 additions and 3 deletions
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1
WHATS_NEW_DM
View File

@ -1,5 +1,6 @@
Version 1.02.136 -
======================================
Fix stats walk segfault with dmsetup older than v1.02.129
Version 1.02.135 - 26th September 2016
======================================

6
libdm/libdm-stats.c
View File

@ -1526,9 +1526,6 @@ static void _stats_walk_end_areas(const struct dm_stats *dms, uint64_t *flags,
static int _stats_walk_end(const struct dm_stats *dms, uint64_t *flags,
uint64_t *cur_r, uint64_t *cur_a, uint64_t *cur_g)
{
if (!dms || !dms->regions)
return 1;
if (*flags & DM_STATS_WALK_AREA) {
_stats_walk_end_areas(dms, flags, cur_r, cur_a, cur_g);
goto out;
@ -1553,6 +1550,9 @@ out:
int dm_stats_walk_end(struct dm_stats *dms)
{
if (!dms || !dms->regions)
return 1;
if (_stats_walk_end(dms, &dms->cur_flags,
&dms->cur_region, &dms->cur_area,
&dms->cur_group)) {