[PATCH 5.10 223/236] x86/resctrl: Fix a maybe-uninitialized build warning treated as error

Greg Kroah-Hartman
2021-09-13T13:50:39Z

From: Babu Moger <babu.moger@amd.com>

commit 527f721478bce3f49b513a733bacd19d6f34b08c upstream.

The recent commit

064855a69003 ("x86/resctrl: Fix default monitoring groups reporting")

caused a RHEL build failure with an uninitialized variable warning
treated as an error because it removed the default case snippet.

The RHEL Makefile uses '-Werror=maybe-uninitialized' to force possibly
uninitialized variable warnings to be treated as errors. This is also
reported by smatch via the 0day robot.

The error from the RHEL build is:

arch/x86/kernel/cpu/resctrl/monitor.c: In function ‘__mon_event_count’:
arch/x86/kernel/cpu/resctrl/monitor.c:261:12: error: ‘m’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
m->chunks += chunks;
^~

The upstream Makefile does not build using '-Werror=maybe-uninitialized'.
So, the problem is not seen there. Fix the problem by putting back the
default case snippet.

[ bp: note that there's nothing wrong with the code and other compilers
do not trigger this warning - this is being done just so the RHEL compiler
is happy. ]

Fixes: 064855a69003 ("x86/resctrl: Fix default monitoring groups reporting")
Reported-by: Terry Bowman <Terry.Bowman@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/162949631908.23903.17090272726012848523.stgit@bmoger-ubuntu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/cpu/resctrl/monitor.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -241,6 +241,12 @@ static u64 __mon_event_count(u32 rmid, s
case QOS_L3_MBM_LOCAL_EVENT_ID:
m = &rr->d->mbm_local[rmid];
break;
+ default:
+ /*
+ * Code would never reach here because an invalid
+ * event id would fail the __rmid_read.
+ */
+ return RMID_VAL_ERROR;
}

if (rr->first) {