[RFC PATCH 1/1] ACPI / APEI: Fix for overwriting aer info when error status data have multiple sections

[shiju.jose]

From: Shiju Jose <shiju.jose@xxxxxxxxxx>

ghes_handle_aer() lacks synchronization with aer_recover_work_func(),
so when error status data have multiple sections, aer_recover_work_func()
may use estatus data for aer_capability_regs after it has been overwritten.

The problem statement is here,
https://lore.kernel.org/all/20230901225755.GA90053@bhelgaas/

In ghes_handle_aer() allocates memory for aer_capability_regs from the
ghes_estatus_pool and copy data for aer_capability_regs from the estatus
buffer. Free the memory in aer_recover_work_func() after processing the
data using the ghes_estatus_pool_region_free() added.

Reported-by: Bjorn Helgaas <helgaas@xxxxxxxxxx>
Signed-off-by: Shiju Jose <shiju.jose@xxxxxxxxxx>
---
 drivers/acpi/apei/ghes.c | 23 ++++++++++++++++++++++-
 drivers/pci/pcie/aer.c   | 10 ++++++++++
 include/acpi/ghes.h      |  1 +
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index ef59d6ea16da..63ad0541db38 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -209,6 +209,20 @@ int ghes_estatus_pool_init(unsigned int num_ghes)
 	return -ENOMEM;
 }
 
+/**
+ * ghes_estatus_pool_region_free - free previously allocated memory
+ *				   from the ghes_estatus_pool.
+ * @addr: address of memory to free.
+ * @size: size of memory to free.
+ *
+ * Returns none.
+ */
+void ghes_estatus_pool_region_free(unsigned long addr, u32 size)
+{
+	gen_pool_free(ghes_estatus_pool, addr, size);
+}
+EXPORT_SYMBOL_GPL(ghes_estatus_pool_region_free);
+
 static int map_gen_v2(struct ghes *ghes)
 {
 	return apei_map_generic_address(&ghes->generic_v2->read_ack_register);
@@ -564,6 +578,7 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
 	    pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO) {
 		unsigned int devfn;
 		int aer_severity;
+		u8 *aer_info;
 
 		devfn = PCI_DEVFN(pcie_err->device_id.device,
 				  pcie_err->device_id.function);
@@ -577,11 +592,17 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
 		if (gdata->flags & CPER_SEC_RESET)
 			aer_severity = AER_FATAL;
 
+		aer_info = (void *)gen_pool_alloc(ghes_estatus_pool,
+						  sizeof(struct aer_capability_regs));
+		if (!aer_info)
+			return;
+		memcpy(aer_info, pcie_err->aer_info, sizeof(struct aer_capability_regs));
+
 		aer_recover_queue(pcie_err->device_id.segment,
 				  pcie_err->device_id.bus,
 				  devfn, aer_severity,
 				  (struct aer_capability_regs *)
-				  pcie_err->aer_info);
+				  aer_info);
 	}
 #endif
 }
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index e85ff946e8c8..388b614c11fd 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -29,6 +29,7 @@
 #include <linux/kfifo.h>
 #include <linux/slab.h>
 #include <acpi/apei.h>
+#include <acpi/ghes.h>
 #include <ras/ras_event.h>
 
 #include "../pci.h"
@@ -996,6 +997,15 @@ static void aer_recover_work_func(struct work_struct *work)
 			continue;
 		}
 		cper_print_aer(pdev, entry.severity, entry.regs);
+		/*
+		 * Memory for aer_capability_regs(entry.regs) is being allocated from the
+		 * ghes_estatus_pool to protect it from overwriting when multiple sections
+		 * are present in the error status. Thus free the same after processing
+		 * the data.
+		 */
+		ghes_estatus_pool_region_free((unsigned long)entry.regs,
+					      sizeof(struct aer_capability_regs));
+
 		if (entry.severity == AER_NONFATAL)
 			pcie_do_recovery(pdev, pci_channel_io_normal,
 					 aer_root_reset);
diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h
index 3c8bba9f1114..40d89e161076 100644
--- a/include/acpi/ghes.h
+++ b/include/acpi/ghes.h
@@ -78,6 +78,7 @@ static inline struct list_head *ghes_get_devices(void) { return NULL; }
 #endif
 
 int ghes_estatus_pool_init(unsigned int num_ghes);
+void ghes_estatus_pool_region_free(unsigned long addr, u32 size);
 
 static inline int acpi_hest_get_version(struct acpi_hest_generic_data *gdata)
 {
-- 
2.34.1