[SRU][R:linux-azure, N:linux-azure][PATCH 1/1] net: mana: Cap MSI-X vectors to the device MSI-X table size

[John Cabaj]

From: Long Li <longli at microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/2169179

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 at microsoft.com>
Reviewed-by: Simon Horman <horms at kernel.org>
Link: https://patch.msgid.link/20260821183736.733296-1-longli@microsoft.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(backported from commit 2c7493f980140a5c40eb4f98f97c557193a2c330)
[john-cabaj: context changes]
Signed-off-by: John Cabaj <john.cabaj at canonical.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 a4fbcde61d2e..2657d124f34f 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -181,6 +181,7 @@ static int mana_gd_query_max_resources(struct pci_dev *pdev)
 	struct gdma_context *gc = pci_get_drvdata(pdev);
 	struct gdma_query_max_resources_resp resp = {};
 	struct gdma_general_req req = {};
+	unsigned int msix_vec_count;
 	int err;
 
 	mana_gd_init_req_hdr(&req.hdr, GDMA_QUERY_MAX_RESOURCES,
@@ -205,6 +206,24 @@ 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;
 
-- 
2.43.0