Each struct ghes has an worst-case sized buffer for storing the
estatus. If an error is being processed by ghes_proc() in process
context this buffer will be in use. If the error source then triggers
an NMI-like notification, the same buffer will be used by
_in_nmi_notify_one() to stage the estatus data, before
__process_error() copys it into a queued estatus entry.

Merge __process_error()s work into _in_nmi_notify_one() so that
the queued estatus entry is used from the beginning. Use the
ghes_peek_estatus() so we know how much memory to allocate from
the ghes_estatus_pool before we read the records.

Reported-by: Borislav Petkov <redacted>
Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/acpi/apei/ghes.c | 45 ++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 055176ed68ac..a0c10b60ad44 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c

@@ -722,40 +722,32 @@ static void ghes_print_queued_estatus(void)
 	}
 }
 
-/* Save estatus for further processing in IRQ context */
-static void __process_error(struct ghes *ghes,
-			    struct acpi_hest_generic_status *ghes_estatus)
+static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
 {
+	u64 buf_paddr;
+	int sev, rc = 0;
 	u32 len, node_len;
 	struct ghes_estatus_node *estatus_node;
 	struct acpi_hest_generic_status *estatus;

+	if (rc)
+		return rc;
 
-	len = cper_estatus_len(ghes_estatus);
 	node_len = GHES_ESTATUS_NODE_LEN(len);
 
 	estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool, node_len);
 	if (!estatus_node)
-		return;
+		return -ENOMEM;
 
 	estatus_node->ghes = ghes;
 	estatus_node->generic = ghes->generic;
 	estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
-	memcpy(estatus, ghes_estatus, len);
-	llist_add(&estatus_node->llnode, &ghes_estatus_llist);
-}
-
-static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
-{
-	int sev;
-	u64 buf_paddr;
-	struct acpi_hest_generic_status *estatus = ghes->estatus;
 
-	if (ghes_read_estatus(ghes, estatus, &buf_paddr, fixmap_idx)) {
+	if (__ghes_read_estatus(estatus, buf_paddr, len, fixmap_idx)) {
 		ghes_clear_estatus(estatus, buf_paddr, fixmap_idx);
-		return -ENOENT;
+		rc = -ENOENT;
+		goto no_work;
 	}
 
 	sev = ghes_severity(estatus->error_severity);

@@ -764,13 +756,20 @@ static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
 		__ghes_panic(ghes, estatus);
 	}
 
-	if (!buf_paddr)
-		return 0;
-
-	__process_error(ghes, estatus);
 	ghes_clear_estatus(estatus, buf_paddr, fixmap_idx);
 
-	return 0;
+	if (!buf_paddr || ghes_estatus_cached(estatus))
+		goto no_work;
+
+	llist_add(&estatus_node->llnode, &ghes_estatus_llist);
+
+	return rc;
+
+no_work:
+	gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node,
+			      node_len);