FAILED: patch "[PATCH] PCI: dwc: ep: Prevent changing BAR size/flags in" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 3708acbd5f169ebafe1faa519cb28adc56295546
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025021044-cruelly-backpack-4cb2@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3708acbd5f169ebafe1faa519cb28adc56295546 Mon Sep 17 00:00:00 2001
From: Niklas Cassel <[email protected]>
Date: Fri, 13 Dec 2024 15:33:03 +0100
Subject: [PATCH] PCI: dwc: ep: Prevent changing BAR size/flags in
pci_epc_set_bar()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

In commit 4284c88fff0e ("PCI: designware-ep: Allow pci_epc_set_bar() update inbound map address") set_bar() was modified to support dynamically changing the backing physical address of a BAR that was already configured.

This means that set_bar() can be called twice, without ever calling clear_bar() (as calling clear_bar() would clear the BAR's PCI address assigned by the host).

This can only be done if the new BAR size/flags does not differ from the existing BAR configuration. Add these missing checks.

If we allow set_bar() to set e.g. a new BAR size that differs from the existing BAR size, the new address translation range will be smaller than the BAR size already determined by the host, which would mean that a read past the new BAR size would pass the iATU untranslated, which could allow the host to read memory not belonging to the new struct pci_epf_bar.

While at it, add comments which clarifies the support for dynamically changing the physical address of a BAR. (Which was also missing.)

index bad588ef69a4..44a617d54b15 100644
@@ -222,8 +222,28 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 	if ((flags & PCI_BASE_ADDRESS_MEM_TYPE_64) && (bar & 1))
 		return -EINVAL;
 
-	if (ep->epf_bar[bar])
+	/*
+	 * Certain EPF drivers dynamically change the physical address of a BAR
+	 * (i.e. they call set_bar() twice, without ever calling clear_bar(), as
+	 * calling clear_bar() would clear the BAR's PCI address assigned by the
+	 * host).
+	 */
+	if (ep->epf_bar[bar]) {
+		/*
+		 * We can only dynamically change a BAR if the new BAR size and
+		 * BAR flags do not differ from the existing configuration.
+		 */
+		if (ep->epf_bar[bar]->barno != bar ||
+		    ep->epf_bar[bar]->size != size ||
+		    ep->epf_bar[bar]->flags != flags)
+			return -EINVAL;
+
+		/*
+		 * When dynamically changing a BAR, skip writing the BAR reg, as
+		 * that would clear the BAR's PCI address assigned by the host.
+		 */
 		goto config_atu;
+	}
 
 	reg = PCI_BASE_ADDRESS_0 + (4 * bar);