[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 <lon...@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