@@ -119,10 +119,15 @@ static ssize_t new_device_store(struct device_driver *driver, const char *buf,
struct platform_device *pdev;
int res, id;
+ if (!try_module_get(THIS_MODULE))
+ return -ENOENT;
+
/* kernfs guarantees string termination, so count + 1 is safe */
aggr = kzalloc(sizeof(*aggr) + count + 1, GFP_KERNEL);
- if (!aggr)
- return -ENOMEM;
+ if (!aggr) {
+ res = -ENOMEM;
+ goto put_module;
+ }
memcpy(aggr->args, buf, count + 1);
@@ -161,6 +166,7 @@ static ssize_t new_device_store(struct device_driver *driver, const char *buf,
}
aggr->pdev = pdev;
+ module_put(THIS_MODULE);
return count;
remove_table:
@@ -175,6 +181,8 @@ static ssize_t new_device_store(struct device_driver *driver, const char *buf,
kfree(aggr->lookups);
free_ga:
kfree(aggr);
+put_module:
+ module_put(THIS_MODULE);
return res;
}
@@ -203,13 +211,19 @@ static ssize_t delete_device_store(struct device_driver *driver,
if (error)
return error;
+ if (!try_module_get(THIS_MODULE))
+ return -ENOENT;
+
mutex_lock(&gpio_aggregator_lock);
aggr = idr_remove(&gpio_aggregator_idr, id);
mutex_unlock(&gpio_aggregator_lock);
- if (!aggr)
+ if (!aggr) {
+ module_put(THIS_MODULE);
return -ENOENT;
+ }
gpio_aggregator_free(aggr);
+ module_put(THIS_MODULE);
return count;
}
static DRIVER_ATTR_WO(delete_device);
Both new_device_store and delete_device_store touch module global resources (e.g. gpio_aggregator_lock). To prevent race conditions with module unload, a reference needs to be held. Add try_module_get() in these handlers. For new_device_store, this eliminates what appears to be the most dangerous scenario: if an id is allocated from gpio_aggregator_idr but platform_device_register has not yet been called or completed, a concurrent module unload could fail to unregister/delete the device, leaving behind a dangling platform device/GPIO forwarder. This can result in various issues. The following simple reproducer demonstrates these problems: #!/bin/bash while :; do # note: whether 'gpiochip0 0' exists or not does not matter. echo 'gpiochip0 0' > /sys/bus/platform/drivers/gpio-aggregator/new_device done & while :; do modprobe gpio-aggregator modprobe -r gpio-aggregator done & wait Starting with the following warning, several kinds of warnings will appear and the system may become unstable: ------------[ cut here ]------------ list_del corruption, ffff888103e2e980->next is LIST_POISON1 (dead000000000100) WARNING: CPU: 1 PID: 1327 at lib/list_debug.c:56 __list_del_entry_valid_or_report+0xa3/0x120 [...] RIP: 0010:__list_del_entry_valid_or_report+0xa3/0x120 [...] Call Trace: <TASK> ? __list_del_entry_valid_or_report+0xa3/0x120 ? __warn.cold+0x93/0xf2 ? __list_del_entry_valid_or_report+0xa3/0x120 ? report_bug+0xe6/0x170 ? __irq_work_queue_local+0x39/0xe0 ? handle_bug+0x58/0x90 ? exc_invalid_op+0x13/0x60 ? asm_exc_invalid_op+0x16/0x20 ? __list_del_entry_valid_or_report+0xa3/0x120 gpiod_remove_lookup_table+0x22/0x60 new_device_store+0x315/0x350 [gpio_aggregator] kernfs_fop_write_iter+0x137/0x1f0 vfs_write+0x262/0x430 ksys_write+0x60/0xd0 do_syscall_64+0x6c/0x180 entry_SYSCALL_64_after_hwframe+0x76/0x7e [...] </TASK> ---[ end trace 0000000000000000 ]--- Fixes: 828546e24280 ("gpio: Add GPIO Aggregator") Signed-off-by: Koichiro Den <koichiro.den@canonical.com> --- drivers/gpio/gpio-aggregator.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)