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R. Silva" To: Bjorn Helgaas , Logan Gunthorpe Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" , linux-hardening@vger.kernel.org Subject: [PATCH v2][next] PCI/P2PDMA: Fix potential undefined behavior bug in struct pci_p2pdma_pagemap Message-ID: MIME-Version: 1.0 Content-Disposition: inline X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Mon, 02 Oct 2023 12:04:27 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1778677945893111241 X-GMAIL-MSGID: 1778677945893111241 `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`. This is currently not the case (notice that `nr_range` is hardcoded to `1`), however as commit b7b3c01b1915 ("mm/memremap_pages: support multiple ranges per invocation") mentions in the subject line, this code can `support multiple ranges per invocation`. So, we'd better prevent any problems that may arise in the future. 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. Reviewed-by: Logan Gunthorpe Signed-off-by: Gustavo A. R. Silva --- Changes in v2: - Remove `Fixes:` tags. (Logan Gunthorpe) - Update changelog text. Make it clear that `nr_range` is hardcoded to `1` (Logan Gunthorpe) - Update subject. - Add Logan's RB. v1: Link: https://lore.kernel.org/linux-hardening/ZRnf6wVOu0IJQ2Ok@work/ 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)