linux-kernel - [PATCH 1/2] EDAC/igen6: Avoid segmentation fault when rmmod

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Message-ID: <20241101204211.414664-2-orange@aiven.io>
Date: Fri,  1 Nov 2024 20:41:13 +0000
From: Orange Kao <orange@...en.io>
To: tony.luck@...el.com,
	qiuxu.zhuo@...el.com
Cc: bp@...en8.de,
	james.morse@....com,
	orange@...sy.org,
	linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mchehab@...nel.org,
	rric@...nel.org,
	Orange Kao <orange@...en.io>
Subject: [PATCH 1/2] EDAC/igen6: Avoid segmentation fault when rmmod

The segmentation fault happens because

During modprobe:
1. In igen6_probe(), igen6_pvt will be allocated with kzalloc()
2. In igen6_register_mci(), mci->pvt_info will point to
   &igen6_pvt->imc[mc]

During rmmod:
1. In mci_release() in edac_mc.c, it will kfree(mci->pvt_info)
2. In igen6_remove(), it will kfree(igen6_pvt);

And that caused double kfree on the same memory address. My proposal is to set
mci->pvt_info to NULL to avoid double-kfree.
---
 drivers/edac/igen6_edac.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/edac/igen6_edac.c b/drivers/edac/igen6_edac.c
index 189a2fc29e74..07dacf8c10be 100644
--- a/drivers/edac/igen6_edac.c
+++ b/drivers/edac/igen6_edac.c
@@ -1245,6 +1245,7 @@ static int igen6_register_mci(int mc, u64 mchbar, struct pci_dev *pdev)
 	imc->mci = mci;
 	return 0;
 fail3:
+	mci->pvt_info = NULL;
 	kfree(mci->ctl_name);
 fail2:
 	edac_mc_free(mci);
@@ -1269,6 +1270,7 @@ static void igen6_unregister_mcis(void)
 
 		edac_mc_del_mc(mci->pdev);
 		kfree(mci->ctl_name);
+		mci->pvt_info = NULL;
 		edac_mc_free(mci);
 		iounmap(imc->window);
 	}
-- 
2.47.0