Messages in this thread | | | Subject | Re: [PATCH v1 2/4] coresight: etm4x: Don't use virtual contextID for non-root PID namespace | From | Suzuki K Poulose <> | Date | Thu, 4 Nov 2021 15:07:45 +0000 |
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Hi Leo
On 31/10/2021 14:42, Leo Yan wrote: > As commented in the function ctxid_pid_store(), it can cause the PID > values mismatching between context ID tracing and PID allocated in a > non-root namespace, and it can leak kernel information. > > For this reason, when a process runs in non-root PID namespace, the > driver doesn't allow contextID tracing and returns failure when access > contextID related sysfs nodes. > > VMID works for virtual contextID when the kernel runs in EL2 mode with > VHE; on the other hand, the driver doesn't prevent users from accessing > it when programs run in the non-root namespace. Thus this can lead > to same issues with contextID described above. > > This patch imposes the checking on VMID related sysfs knobs, it returns > failure if current process runs in non-root PID namespace. > > Signed-off-by: Leo Yan <leo.yan@linaro.org>
Patch looks good to me. Please see minor comment below.
> --- > .../coresight/coresight-etm4x-sysfs.c | 28 +++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c > index e4c8c44d04ef..e218281703b0 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c > @@ -2111,6 +2111,13 @@ static ssize_t vmid_val_show(struct device *dev, > struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent); > struct etmv4_config *config = &drvdata->config; > > + /* > + * Don't use virtual contextID tracing if coming from a PID namespace. > + * See comment in ctxid_pid_store(). > + */ > + if (task_active_pid_ns(current) != &init_pid_ns) > + return -EINVAL; > + > spin_lock(&drvdata->spinlock); > val = (unsigned long)config->vmid_val[config->vmid_idx]; > spin_unlock(&drvdata->spinlock); > @@ -2125,6 +2132,13 @@ static ssize_t vmid_val_store(struct device *dev, > struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent); > struct etmv4_config *config = &drvdata->config; > > + /* > + * Don't use virtual contextID tracing if coming from a PID namespace. > + * See comment in ctxid_pid_store(). > + */ > + if (task_active_pid_ns(current) != &init_pid_ns)
Please could we add a helper function to make this obvious ?
e.g: task_is_in_root_ns(task) ?
Suzuki
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