[PULL,26/55] hw/vfio/pci: Fix missing ERRP_GUARD() for error_prepend()

Commit Message

Thomas Huth March 12, 2024, 12:43 p.m. UTC

From: Zhao Liu <[e-mail]>

As the comment in qapi/error, passing @errp to error_prepend() requires
ERRP_GUARD():

* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
...
* - It should not be passed to error_prepend(), error_vprepend() or
*   error_append_hint(), because that doesn't work with &error_fatal.
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.

ERRP_GUARD() could avoid the case when @errp is &error_fatal, the user
can't see this additional information, because exit() happens in
error_setg earlier than information is added [1].

In hw/vfio/pci.c, there are 2 functions passing @errp to error_prepend()
without ERRP_GUARD():
- vfio_add_std_cap()
- vfio_realize()

The @errp of vfio_add_std_cap() is also from vfio_realize(). And
vfio_realize(), as a PCIDeviceClass.realize method, its @errp is from
DeviceClass.realize so that there is no guarantee that the @errp won't
point to @error_fatal.

To avoid the issue like [1] said, add missing ERRP_GUARD() at their
beginning.

[1]: Issue description in the commit message of commit ae7c80a7bd73
     ("error: New macro ERRP_GUARD()").

Cc: Alex Williamson <[e-mail]>
Cc: Cédric Le Goater <[e-mail]>
Signed-off-by: Zhao Liu <[e-mail]>
Reviewed-by: Cédric Le Goater <[e-mail]>
Message-ID: <[e-mail]>
Signed-off-by: Thomas Huth <[e-mail]>
---
 hw/vfio/pci.c | 2 ++
 1 file changed, 2 insertions(+)

Patch

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index a1522a011a..64780d1b79 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2136,6 +2136,7 @@  static void vfio_check_af_flr(VFIOPCIDevice *vdev, uint8_t pos)
 
 static int vfio_add_std_cap(VFIOPCIDevice *vdev, uint8_t pos, Error **errp)
 {
+    ERRP_GUARD();
     PCIDevice *pdev = &vdev->pdev;
     uint8_t cap_id, next, size;
     int ret;
@@ -2942,6 +2943,7 @@  static void vfio_unregister_req_notifier(VFIOPCIDevice *vdev)
 
 static void vfio_realize(PCIDevice *pdev, Error **errp)
 {
+    ERRP_GUARD();
     VFIOPCIDevice *vdev = VFIO_PCI(pdev);
     VFIODevice *vbasedev = &vdev->vbasedev;
     char *tmp, *subsys;