[PATCH v3 09/10] ACPI: APEI: GHES: Bound AER info copy and sanitize software metadata

sashiko-bot flagged that ghes_handle_aer() has the same unvalidated
AER buffer handling plus a 4-byte over-read.

ghes_handle_aer() copies sizeof(struct aer_capability_regs) from the
fixed 96-byte pcie_err->aer_info, reading past the section since the
struct is larger. It also fills the software-only header_len and flit
fields of the embedded struct pcie_tlp_log from raw firmware bytes;
pcie_print_tlp_log() uses them to bound a loop over dw[], so a large
value walks past the array. There is also no check that the section can
hold a struct cper_sec_pcie.

Validate error_data_length, zero the destination, bound the copy to the
96-byte source, and clear header_len and flit. This mirrors the
extlog_print_pcie() fix.

Reported-by: [email protected]
Closes: https://sashiko.dev/#/patchset/[email protected]?part=3
Fixes: 7e077e6707b3 ("PCI/ERR: Handle TLP Log in Flit mode")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Dave Jiang <[email protected]>
---
v3:
- New patch. sashiko's review of v2 flagged the same unvalidated AER
  buffer handling in ghes_handle_aer() that v2 fixed for extlog.
---
 drivers/acpi/apei/ghes.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 1d2966a437bd..bd53509dcab3 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -642,11 +642,14 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
 #ifdef CONFIG_ACPI_APEI_PCIEAER
 	struct cper_sec_pcie *pcie_err = acpi_hest_get_payload(gdata);
 
+	if (gdata->error_data_length < sizeof(*pcie_err))
+		return;
+
 	if (pcie_err->validation_bits & CPER_PCIE_VALID_DEVICE_ID &&
 	    pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO) {
+		struct aer_capability_regs *aer_info;
 		unsigned int devfn;
 		int aer_severity;
-		u8 *aer_info;
 
 		devfn = PCI_DEVFN(pcie_err->device_id.device,
 				  pcie_err->device_id.function);
@@ -664,13 +667,22 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
 						  sizeof(struct aer_capability_regs));
 		if (!aer_info)
 			return;
-		memcpy(aer_info, pcie_err->aer_info, sizeof(struct aer_capability_regs));
+
+		/*
+		 * aer_info is a fixed 96-byte buffer, smaller than struct
+		 * aer_capability_regs, so bound the copy to the source. Clear
+		 * the software-only header_len and flit fields afterwards so
+		 * firmware bytes cannot drive the pcie_print_tlp_log() loop over
+		 * dw[] out of bounds.
+		 */
+		memset(aer_info, 0, sizeof(struct aer_capability_regs));
+		memcpy(aer_info, pcie_err->aer_info, sizeof(pcie_err->aer_info));
+		aer_info->header_log.header_len = 0;
+		aer_info->header_log.flit = false;
 
 		aer_recover_queue(pcie_err->device_id.segment,
 				  pcie_err->device_id.bus,
-				  devfn, aer_severity,
-				  (struct aer_capability_regs *)
-				  aer_info);
+				  devfn, aer_severity, aer_info);
 	}
 #endif
 }
-- 
2.55.0