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perf/x86/intel: Fix LBR callstack issue caused by FREEZE_LBRS_ON_PMI

DISCUSSION Dan Carpenter 2 participants 2 messages Sep 14, 2015 Kernel janitors

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Dan Carpenter

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#0 lore raw

Hello Kan Liang,

This is a semi-automatic email about new static checker warnings.

The patch deb27519bf1f: "perf/x86/intel: Fix LBR callstack issue caused by FREEZE_LBRS_ON_PMI" from Aug 17, 2015, leads to the following Smatch complaint:

arch/x86/kernel/cpu/perf_event_intel_lbr.c:155 __intel_pmu_lbr_enable()

	 warn: variable dereferenced before check 'cpuc->lbr_sel' (see line 154)

arch/x86/kernel/cpu/perf_event_intel_lbr.c
153 */

   154		lbr_select = cpuc->lbr_sel->config;
                             ^^^^^^^^^^^^^^^^^^^^^

New unchecked dereference.

155 if (cpuc->lbr_sel && !pmi)

                    ^^^^^^^^^^^^^

Old code assumes it can be NULL.

   156			wrmsrl(MSR_LBR_SELECT, lbr_select);
   157

regards,
dan carpenter

#1 lore raw
Quoted 19 lines

Hello Kan Liang,

This is a semi-automatic email about new static checker warnings.

The patch deb27519bf1f: "perf/x86/intel: Fix LBR callstack issue caused by FREEZE_LBRS_ON_PMI" from Aug 17, 2015, leads to the following Smatch complaint:

arch/x86/kernel/cpu/perf_event_intel_lbr.c:155 __intel_pmu_lbr_enable()

	 warn: variable dereferenced before check 'cpuc->lbr_sel' (see line

154)

arch/x86/kernel/cpu/perf_event_intel_lbr.c
153 */

   154		lbr_select = cpuc->lbr_sel->config;
                             ^^^^^^^^^^^^^^^^^^^^^ New unchecked dereference.
Quoted 7 lines
   155		if (cpuc->lbr_sel && !pmi)
                    ^^^^^^^^^^^^^

Old code assumes it can be NULL.

   156			wrmsrl(MSR_LBR_SELECT, lbr_select);
   157

Thanks.
I will send out a new patch to fix it.

Regards,
Kan

Quoted 2 lines

regards,
dan carpenter