perf/arm-cmn: Fix invalid pointer when access dtc object sharing the same IRQ number

[ Upstream commit 4e16f283edc289820e9b2d6f617ed8e514ee8396 ]

When multiple dtcs share the same IRQ number, the irq_friend which
used to refer to dtc object gets calculated incorrect which leads
to invalid pointer.

Fixes: 0ba64770a2f2 ("perf: Add Arm CMN-600 PMU driver")
Signed-off-by: Tuan Phan <tuanphan@os.amperecomputing.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/1623946129-3290-1-git-send-email-tuanphan@os.amperecomputing.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 1328159fe564d6187177ce1d73bc9ccff18d6835..a4339426664e54517b0eb25111bf8af1304c3a75 100644 (file)
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1212,7 +1212,7 @@ static int arm_cmn_init_irqs(struct arm_cmn *cmn)
                irq = cmn->dtc[i].irq;
                for (j = i; j--; ) {
                        if (cmn->dtc[j].irq == irq) {
-                               cmn->dtc[j].irq_friend = j - i;
+                               cmn->dtc[j].irq_friend = i - j;
                                goto next;
                        }
                }