linux-kernel - [PATCH][next] PCI/P2PDMA: Fix undefined behavior bug in struct pci_p2pdma

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Message-ID: <ZRnf6wVOu0IJQ2Ok@work>
Date:   Sun, 1 Oct 2023 23:08:59 +0200
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] PCI/P2PDMA: Fix undefined behavior bug in struct
 pci_p2pdma_pagemap

`struct dev_pagemap` is a flexible structure, which means that it
contains a flexible-array member at the bottom. This could potentially
lead to an overwrite of the objects following `pgmap` in `struct
pci_p2pdma_pagemap`, when `nr_range > 1`.

Fix this by placing the declaration of object `pgmap` at the end of
`struct pci_p2pdma_pagemap`.

-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.

Fixes: 0afea3814358 ("PCI/P2PDMA: Add provider's pci_dev to pci_p2pdma_pagemap struct")
Fixes: a6e6fe6549f6 ("PCI/P2PDMA: Introduce private pagemap structure")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/pci/p2pdma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index fa7370f9561a..ab34d3d36a64 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -28,9 +28,9 @@ struct pci_p2pdma {
 };
 
 struct pci_p2pdma_pagemap {
-	struct dev_pagemap pgmap;
 	struct pci_dev *provider;
 	u64 bus_offset;
+	struct dev_pagemap pgmap;
 };
 
 static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)
-- 
2.34.1