From f3b8172fe15fbed0d0d33d99780e122213e00684 Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose Date: Tue, 14 Jun 2016 11:17:14 -0600 Subject: [PATCH] coresight: Fix erroneous memset in tmc_read_unprepare_etr At the end of a trace collection, we try to clear the entire buffer and enable the ETR back if it was already enabled. But, we would have adjusted the drvdata->buf to point to the beginning of the trace data in the trace buffer @drvdata->vaddr. So, the following code which clears the buffer is dangerous and can cause crashes, like below : memset(drvdata->buf, 0, drvdata->size); Unable to handle kernel paging request at virtual address ffffff800a145000 pgd = ffffffc974726000 *pgd=00000009f3e91003, *pud=00000009f3e91003, *pmd=0000000000000000 PREEMPT SMP Modules linked in: CPU: 4 PID: 1692 Comm: dd Not tainted 4.7.0-rc2+ #1721 Hardware name: ARM Juno development board (r0) (DT) task: ffffffc9734a0080 ti: ffffffc974460000 task.ti: ffffffc974460000 PC is at __memset+0x1ac/0x200 LR is at tmc_read_unprepare_etr+0x144/0x1bc pc : [] lr : [] pstate: 200001c5 ... [] __memset+0x1ac/0x200 [] tmc_release+0x90/0x94 [] __fput+0xa8/0x1ec [] ____fput+0xc/0x14 [] task_work_run+0xb0/0xe4 [] do_notify_resume+0x64/0x6c [] work_pending+0x10/0x14 Code: 91010108 54ffff4a 8b040108 cb050042 (d50b7428) Since we clear the buffer anyway in the following call to tmc_etr_enable_hw(), remove the erroneous memset(). Fixes: commit de5461970b3e9e1 ("coresight: tmc: allocating memory when needed") Cc: Mathieu Poirier Signed-off-by: Suzuki K Poulose Signed-off-by: Mathieu Poirier Signed-off-by: Greg Kroah-Hartman --- drivers/hwtracing/coresight/coresight-tmc-etr.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 3369d7a..688be9e 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -300,13 +300,10 @@ int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata) if (local_read(&drvdata->mode) == CS_MODE_SYSFS) { /* * The trace run will continue with the same allocated trace - * buffer. As such zero-out the buffer so that we don't end - * up with stale data. - * - * Since the tracer is still enabled drvdata::buf - * can't be NULL. + * buffer. The trace buffer is cleared in tmc_etr_enable_hw(), + * so we don't have to explicitly clear it. Also, since the + * tracer is still enabled drvdata::buf can't be NULL. */ - memset(drvdata->buf, 0, drvdata->size); tmc_etr_enable_hw(drvdata); } else { /* -- 2.7.4