Hi Greg,

On Mon, Jul 01, 2024 at 04:22:20PM +0200, gregkh@linuxfoundation.org wrote:

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.

I can’t repro the UAF in 6.1. Looking more, I think the bug was actual introduced when MSI_COMMON_FLAGS was added with MSI_FLAG_FREE_MSI_DESCS in commit "a737b7d0e721 (PCI/MSI: Add support for per device MSI[X] domains)"

And not from the freeing logic mentioned in the Fixes, so the first affected version is 6.2

Thanks, Mostafa

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;