FAILED: patch "[PATCH] PCI/MSI: Fix UAF in msi_capability_init" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-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 <stable@vger.kernel.org>.

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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 9eee5330656bf92f51cb1f09b2dc9f8cf975b3d1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024070120-undergo-stipulate-9aae@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

9eee5330656b ("PCI/MSI: Fix UAF in msi_capability_init")
b12d0bec385b ("PCI/MSI: Move pci_disable_msi() to api.c")
c93fd5266cff ("PCI/MSI: Move mask and unmask helpers to msi.h")
a474d3fbe287 ("PCI/MSI: Get rid of PCI_MSI_IRQ_DOMAIN")

thanks,

greg k-h

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

From 9eee5330656bf92f51cb1f09b2dc9f8cf975b3d1 Mon Sep 17 00:00:00 2001
From: Mostafa Saleh <smostafa@google.com>
Date: Mon, 24 Jun 2024 20:37:28 +0000
Subject: [PATCH] PCI/MSI: Fix UAF in msi_capability_init

KFENCE reports the following UAF:

 BUG: KFENCE: use-after-free read in __pci_enable_msi_range+0x2c0/0x488

 Use-after-free read at 0x0000000024629571 (in kfence-#12):
  __pci_enable_msi_range+0x2c0/0x488
  pci_alloc_irq_vectors_affinity+0xec/0x14c
  pci_alloc_irq_vectors+0x18/0x28

 kfence-#12: 0x0000000008614900-0x00000000e06c228d, size=104, cache=kmalloc-128

 allocated by task 81 on cpu 7 at 10.808142s:
  __kmem_cache_alloc_node+0x1f0/0x2bc
  kmalloc_trace+0x44/0x138
  msi_alloc_desc+0x3c/0x9c
  msi_domain_insert_msi_desc+0x30/0x78
  msi_setup_msi_desc+0x13c/0x184
  __pci_enable_msi_range+0x258/0x488
  pci_alloc_irq_vectors_affinity+0xec/0x14c
  pci_alloc_irq_vectors+0x18/0x28

 freed by task 81 on cpu 7 at 10.811436s:
  msi_domain_free_descs+0xd4/0x10c
  msi_domain_free_locked.part.0+0xc0/0x1d8
  msi_domain_alloc_irqs_all_locked+0xb4/0xbc
  pci_msi_setup_msi_irqs+0x30/0x4c
  __pci_enable_msi_range+0x2a8/0x488
  pci_alloc_irq_vectors_affinity+0xec/0x14c
  pci_alloc_irq_vectors+0x18/0x28

Descriptor allocation done in:
__pci_enable_msi_range
    msi_capability_init
        msi_setup_msi_desc
            msi_insert_msi_desc
                msi_domain_insert_msi_desc
                    msi_alloc_desc
                        ...

Freed in case of failure in __msi_domain_alloc_locked()
__pci_enable_msi_range
    msi_capability_init
        pci_msi_setup_msi_irqs
            msi_domain_alloc_irqs_all_locked
                msi_domain_alloc_locked
                    __msi_domain_alloc_locked => fails
                    msi_domain_free_locked
                        ...

That failure propagates back to pci_msi_setup_msi_irqs() in
msi_capability_init() which accesses the descriptor for unmasking in the
error exit path.

Cure it by copying the descriptor and using the copy for the error exit path
unmask operation.

[ tglx: Massaged change log ]

Fixes: bf6e054e0e3f ("genirq/msi: Provide msi_device_populate/destroy_sysfs()")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Heelgas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240624203729.1094506-1-smostafa@google.com

diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
index c5625dd9bf49..3a45879d85db 100644
--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -352,7 +352,7 @@ static int msi_capability_init(struct pci_dev *dev, int nvec,
 			       struct irq_affinity *affd)
 {
 	struct irq_affinity_desc *masks = NULL;
-	struct msi_desc *entry;
+	struct msi_desc *entry, desc;
 	int ret;
 
 	/* Reject multi-MSI early on irq domain enabled architectures */
@@ -377,6 +377,12 @@ static int msi_capability_init(struct pci_dev *dev, int nvec,
 	/* All MSIs are unmasked by default; mask them all */
 	entry = msi_first_desc(&dev->dev, MSI_DESC_ALL);
 	pci_msi_mask(entry, msi_multi_mask(entry));
+	/*
+	 * Copy the MSI descriptor for the error path because
+	 * pci_msi_setup_msi_irqs() will free it for the hierarchical
+	 * interrupt domain case.
+	 */
+	memcpy(&desc, entry, sizeof(desc));
 
 	/* Configure MSI capability structure */
 	ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSI);
@@ -396,7 +402,7 @@ static int msi_capability_init(struct pci_dev *dev, int nvec,
 	goto unlock;
 
 err:
-	pci_msi_unmask(entry, msi_multi_mask(entry));
+	pci_msi_unmask(&desc, msi_multi_mask(&desc));
 	pci_free_msi_irqs(dev);
 fail:
 	dev->msi_enabled = 0;