[dpdk-dev] [PATCH v3] dev: don't remove devargs that are still referenced
Maxime Coquelin
maxime.coquelin at redhat.com
Fri Nov 23 18:04:44 CET 2018
Hi,
On 11/23/18 4:43 PM, Darek Stojaczyk wrote:
> Even if a device failed to plug, it's still a device
> object that references the devargs. Those devargs will
> be freed automatically together with the device, but
> freeing them any earlier - like it's done in the hotplug
> error handling path right now - will give us a dangling
> pointer and a segfault scenario.
>
> Consider the following case:
> * secondary process receives the hotplug request IPC message
> * devargs are either created or updated
> * the bus is scanned
> * a new device object is created with the latest devargs
> * the device can't be plugged for whatever reason,
> bus->plug returns error
> * the devargs are freed, even though they're still referenced
> by the device object on the bus
>
> For PCI devices, the generic device name comes from
> a buffer within the devargs. Freeing those will make
> EAL segfault whenever the device name is checked.
>
> This patch just prevents the hotplug error handling
> path from removing the devargs when there's a device
> that references them. This is done by simply exiting
> early from the hotplug function. As mentioned in the
> beginning, those devargs will be freed later, together
> with the device itself.
>
> Fixes: 7e8b26650146 ("eal: fix hotplug add / remove")
Should you also cc stable?
Above commit is in since v17.08.
> Cc: gaetan.rivet at 6wind.com
> Cc: thomas at monjalon.net
>
> Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk at intel.com>
> ---
> Changes since v2:
> * added an extra comment (Gaetan)
>
> Changes since v1:
> * described the failing scenario in commit msg (Thomas)
>
> lib/librte_eal/common/eal_common_dev.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_dev.c b/lib/librte_eal/common/eal_common_dev.c
> index 1fdc9ab17..d7950bc9a 100644
> --- a/lib/librte_eal/common/eal_common_dev.c
> +++ b/lib/librte_eal/common/eal_common_dev.c
> @@ -166,14 +166,17 @@ local_dev_probe(const char *devargs, struct rte_device **new_dev)
> ret = -ENODEV;
> goto err_devarg;
> }
> + /* Since there is a matching device, it is now its responsibility
> + * to manage the devargs we've just inserted. From this point
> + * those devargs shouldn't be removed manually anymore.
> + */
>
> ret = dev->bus->plug(dev);
> if (ret) {
> - if (rte_dev_is_probed(dev)) /* if already succeeded earlier */
> - return ret; /* no rollback */
> - RTE_LOG(ERR, EAL, "Driver cannot attach the device (%s)\n",
> - dev->name);
> - goto err_devarg;
> + if (!rte_dev_is_probed(dev)) /* if hasn't succeeded earlier */
> + RTE_LOG(ERR, EAL, "Driver cannot attach the device (%s)\n",
> + dev->name);
> + return ret;
> }
>
> *new_dev = dev;
>
Other than that, it looks good to me:
Acked-by: Maxime Coquelin <maxime.coquelin at redhat.com>
Regards,
Maxime
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