linux-kernel - [PATCH V9] devcoredump: add context check in dev

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Message-Id: <20220926061609.44153-1-duoming@zju.edu.cn>
Date:   Mon, 26 Sep 2022 14:16:09 +0800
From:   Duoming Zhou <duoming@....edu.cn>
To:     johannes@...solutions.net, gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, rafael@...nel.org,
        Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH V9] devcoredump: add context check in dev_coredumpm

The dev_coredumpm(), dev_coredumpv() and dev_coredumpsg() could not
be used in atomic context, because they call kvasprintf_const() and
kstrdup() with GFP_KERNEL parameter. The process is shown below:

dev_coredumpv(.., gfp_t gfp)
  dev_coredumpm(.., gfp_t gfp)
    dev_set_name
      kobject_set_name_vargs
        kvasprintf_const(GFP_KERNEL, ...); //may sleep
          kstrdup(s, GFP_KERNEL); //may sleep

This patch adds context check in dev_coredumpm() in order to show
dev_coredumpm() and its callers could not be used in atomic context.

What's more, this change can allow the api to evolve and will not
influence the users that call this api.

Fixes: 833c95456a70 ("device coredump: add new device coredump class")
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
Changes in v9:
  - Add context check in dev_coredumpm().

 drivers/base/devcoredump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
index f4d794d6bb8..806ee872f5f 100644
--- a/drivers/base/devcoredump.c
+++ b/drivers/base/devcoredump.c
@@ -255,6 +255,9 @@ void dev_coredumpm(struct device *dev, struct module *owner,
 	struct devcd_entry *devcd;
 	struct device *existing;
 
+	if (!gfpflags_normal_context(gfp))
+		goto free;
+
 	if (devcd_disabled)
 		goto free;
 
-- 
2.17.1