[PATCH net] net: mana: Cap MSI-X vectors to the device MSI-X table size

[PATCH net] net: mana: Cap MSI-X vectors to the device MSI-X table size

[Long Li]

mana_gd_query_max_resources() sizes gc->num_msix_usable from resp.max_msix
and the CPU count, but never from the device MSI-X table. On a 1792 vCPU
M-series VM that yields 1793 while the table has 1024 entries, and
mana_gd_setup_remaining_irqs() then walks indices 1..1792, running off the
end of the region mapped by msix_map_region():

  BUG: unable to handle page fault for address: ff8e347f8b99800c
  RIP: 0010:msix_prepare_msi_desc+0x7a/0x90
  RAX: 0000000000004000 RBX: ff4330cb164ea780 RCX: ff8e347f8b998000
  Call Trace:
   <TASK>
   __msi_domain_alloc_irqs+0x13a/0x440
   msi_domain_alloc_irq_at+0x149/0x1b0
   mana_gd_setup+0x351/0x890
   mana_gd_probe+0x274/0x390
   </TASK>

RAX is index 1024 * PCI_MSIX_ENTRY_SIZE, one entry past the table.

msi_insert_desc() does range check the index, but only against the MSI
domain hwsize, which matches the table only for devices on an MSI parent
domain. With a global PCI/MSI domain hwsize is MSI_XA_DOMAIN_SIZE, so
nothing bounds the request.

Cap num_msix_usable with pci_msix_vec_count().

Fixes: 755391121038 ("net: mana: Allocate MSI-X vectors dynamically")
Signed-off-by: Long Li <longli@microsoft.com>
---
 .../net/ethernet/microsoft/mana/gdma_main.c   | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index ed9af314e4ede3ea0422694bd1f2f652f9c10478..f92b2d0bf926e1b715ff665d37f8173a2103e6fe 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -182,6 +182,7 @@ static int mana_gd_query_max_resources(struct pci_dev *pdev)
 	struct gdma_query_max_resources_resp resp = {};
 	struct gdma_general_req req = {};
 	unsigned int max_num_queues;
+	unsigned int msix_vec_count;
 	u8 bm_hostmode;
 	u16 num_ports;
 	int err;
@@ -218,6 +219,24 @@ static int mana_gd_query_max_resources(struct pci_dev *pdev)
 		gc->num_msix_usable = min(resp.max_msix, num_online_cpus() + 1);
 	}
 
+	/* MSI-X vectors are allocated by index into the device MSI-X table, so
+	 * never ask for more than the table holds. It can be smaller than both
+	 * resp.max_msix and the CPU count.
+	 */
+	err = pci_msix_vec_count(pdev);
+	if (err <= 0) {
+		dev_err(gc->dev, "Failed to query MSI-X table size: %d\n", err);
+		return err < 0 ? err : -ENOSPC;
+	}
+	msix_vec_count = err;
+
+	if (gc->num_msix_usable > msix_vec_count) {
+		dev_info(gc->dev,
+			 "Limiting MSI-X vectors from %u to table size %u\n",
+			 gc->num_msix_usable, msix_vec_count);
+		gc->num_msix_usable = msix_vec_count;
+	}
+
 	if (gc->num_msix_usable <= 1)
 		return -ENOSPC;
 

base-commit: 746fc0787f616da418ffc04a110296fe95d53491
-- 
2.43.0

Re: [PATCH net] net: mana: Cap MSI-X vectors to the device MSI-X table size

[Simon Horman]

On Fri, Aug 21, 2026 at 11:37:36AM -0700, Long Li wrote:
> mana_gd_query_max_resources() sizes gc->num_msix_usable from resp.max_msix
> and the CPU count, but never from the device MSI-X table. On a 1792 vCPU
> M-series VM that yields 1793 while the table has 1024 entries, and
> mana_gd_setup_remaining_irqs() then walks indices 1..1792, running off the
> end of the region mapped by msix_map_region():
> 
>   BUG: unable to handle page fault for address: ff8e347f8b99800c
>   RIP: 0010:msix_prepare_msi_desc+0x7a/0x90
>   RAX: 0000000000004000 RBX: ff4330cb164ea780 RCX: ff8e347f8b998000
>   Call Trace:
>    <TASK>
>    __msi_domain_alloc_irqs+0x13a/0x440
>    msi_domain_alloc_irq_at+0x149/0x1b0
>    mana_gd_setup+0x351/0x890
>    mana_gd_probe+0x274/0x390
>    </TASK>
> 
> RAX is index 1024 * PCI_MSIX_ENTRY_SIZE, one entry past the table.
> 
> msi_insert_desc() does range check the index, but only against the MSI
> domain hwsize, which matches the table only for devices on an MSI parent
> domain. With a global PCI/MSI domain hwsize is MSI_XA_DOMAIN_SIZE, so
> nothing bounds the request.
> 
> Cap num_msix_usable with pci_msix_vec_count().
> 
> Fixes: 755391121038 ("net: mana: Allocate MSI-X vectors dynamically")
> Signed-off-by: Long Li <longli@microsoft.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] net: mana: Cap MSI-X vectors to the device MSI-X table size

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 21 Aug 2026 11:37:36 -0700 you wrote:
> mana_gd_query_max_resources() sizes gc->num_msix_usable from resp.max_msix
> and the CPU count, but never from the device MSI-X table. On a 1792 vCPU
> M-series VM that yields 1793 while the table has 1024 entries, and
> mana_gd_setup_remaining_irqs() then walks indices 1..1792, running off the
> end of the region mapped by msix_map_region():
> 
>   BUG: unable to handle page fault for address: ff8e347f8b99800c
>   RIP: 0010:msix_prepare_msi_desc+0x7a/0x90
>   RAX: 0000000000004000 RBX: ff4330cb164ea780 RCX: ff8e347f8b998000
>   Call Trace:
>    <TASK>
>    __msi_domain_alloc_irqs+0x13a/0x440
>    msi_domain_alloc_irq_at+0x149/0x1b0
>    mana_gd_setup+0x351/0x890
>    mana_gd_probe+0x274/0x390
>    </TASK>
> 
> [...]

Here is the summary with links:
  - [net] net: mana: Cap MSI-X vectors to the device MSI-X table size
    https://git.kernel.org/netdev/net/c/2c7493f98014

You are awesome, thank you!
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