rpci: Use pci_dev struct pointer to avoid API breaks

The pci_dev structure is never meant to be used as is, but always as a
pointer. By using the struct itself in undo_pci_write_data, we are risking
data corruption, or buffer overflows if the structure size changes.

This is especially apparent on my system where flashrom segfaults
because I compile it with pciutils 3.3.0 and I run it on a system
with pciutils 3.5.2. The struture size is different and causes a
struct with the wrong size to be sent to the library, with invalid
internal field values.

This has been discovered and discussed in Change ID 18925 [1]

[1] https://review.coreboot.org/#/c/18925/

Change-Id: Icde2e587992ba964d4ff92c33aa659850ba06298
Signed-off-by: Youness Alaoui <kakaroto@kakaroto.homelinux.net>
Reviewed-on: https://review.coreboot.org/20784
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/chipset_enable.c b/chipset_enable.c
index 20d266200..6a93d0d57 100644
--- a/chipset_enable.c
+++ b/chipset_enable.c
@@ -843,6 +843,7 @@ static int enable_flash_pch100(struct pci_dev *const dev, const char *const name
 	 * straints (e.g. on PCI domains, extended PCIe config space).
 	 */
 	struct pci_access *const pci_acc = pci_alloc();
+	struct pci_access *const saved_pacc = pacc;
 	if (!pci_acc) {
 		msg_perr("Can't allocate PCI accessor.\n");
 		return ret;
@@ -857,6 +858,9 @@ static int enable_flash_pch100(struct pci_dev *const dev, const char *const name
 		return ret;
 	}
 
+	/* Modify pacc so the rpci_write can register the undo callback with a
+	 * device using the correct pci_access */
+	pacc = pci_acc;
 	enable_flash_ich_report_gcs(spi_dev, pch_generation, NULL);
 
 	const int ret_bc = enable_flash_ich_bios_cntl_config_space(spi_dev, pch_generation, 0xdc);
@@ -880,6 +884,7 @@ static int enable_flash_pch100(struct pci_dev *const dev, const char *const name
 
 _freepci_ret:
 	pci_free_dev(spi_dev);
+	pacc = saved_pacc;
 	return ret;
 }