From bd9eb7fbe69111ea0ff1f999ef4a5f26d223d1d5 Mon Sep 17 00:00:00 2001 From: Chuansheng Liu Date: Sat, 10 Nov 2012 01:27:22 +0800 Subject: [PATCH] firmware loader: Fix the concurrent request_firmware() race for kref_get/put There is one race that both request_firmware() with the same firmware name. The race scenerio is as below: CPU1 CPU2 request_firmware() --> _request_firmware_load() return err another request_firmware() is coming --> _request_firmware_cleanup is called --> _request_firmware_prepare --> release_firmware ---> fw_lookup_and_allocate_buf --> spin_lock(&fwc->lock) ... __fw_lookup_buf() return true fw_free_buf() will be called --> ... kref_put --> decrease the refcount to 0 kref_get(&tmp->ref) ==> it will trigger warning due to refcount == 0 __fw_free_buf() --> ... spin_unlock(&fwc->lock) spin_lock(&fwc->lock) list_del(&buf->list) spin_unlock(&fwc->lock) kfree(buf) After that, the freed buf will be used. The key race is decreasing refcount to 0 and list_del is not protected together by fwc->lock, and it is possible another thread try to get it between refcount==0 and list_del. Fix it here to protect it together. Acked-by: Ming Lei Signed-off-by: liu chuansheng Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/base/firmware_class.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c index b44ed35..be5f7aa 100644 --- a/drivers/base/firmware_class.c +++ b/drivers/base/firmware_class.c @@ -246,7 +246,6 @@ static void __fw_free_buf(struct kref *ref) __func__, buf->fw_id, buf, buf->data, (unsigned int)buf->size); - spin_lock(&fwc->lock); list_del(&buf->list); spin_unlock(&fwc->lock); @@ -263,7 +262,10 @@ static void __fw_free_buf(struct kref *ref) static void fw_free_buf(struct firmware_buf *buf) { - kref_put(&buf->ref, __fw_free_buf); + struct firmware_cache *fwc = buf->fwc; + spin_lock(&fwc->lock); + if (!kref_put(&buf->ref, __fw_free_buf)) + spin_unlock(&fwc->lock); } /* direct firmware loading support */ -- 2.7.4