[10/17] hw/vfio/pci: Fix missing ERRP_GUARD() for error_prepend()

Commit Message

Zhao Liu Feb. 29, 2024, 2:39 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 the pointer of
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're 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]>
---
 hw/vfio/pci.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Cédric Le Goater Feb. 29, 2024, 6:25 p.m. UTC | #1

On 2/29/24 15:39, Zhao Liu wrote:
> 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 the pointer of
> 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're 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]>

Thanks,

C.

Patch

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 4fa387f0430d..e70efde11913 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;