On 04/07/2023 18:54, Cédric Le Goater wrote:
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Hello Avihai
On 7/4/23 15:39, Avihai Horon wrote:
vfio_realize() has the following flow:
1. vfio_bars_prepare() -- sets VFIOBAR->size.
2. msix_early_setup().
3. vfio_bars_register() -- allocates VFIOBAR->mr.
After vfio_bars_prepare() is called msix_early_setup() can fail. If it
does fail, vfio_bars_register() is never called and VFIOBAR->mr is not
allocated.
In this case, vfio_bars_finalize() is called as part of the error flow
to free the bars' resources. However, vfio_bars_finalize() calls
object_unparent() for VFIOBAR->mr after checking only VFIOBAR->size, and
thus we get a null pointer dereference.
Fix it by checking VFIOBAR->mr in vfio_bars_finalize().
Did you see the issue by reading the code or did you actually crash
QEMU with a test case ?
I actually got a segmentation fault after msix_early_setup() failed (due
to some other misconfiguration from my side).
Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO")
Signed-off-by: Avihai Horon <avih...@nvidia.com>
Reviewed-by: Cédric Le Goater <c...@redhat.com>
Thanks,
C.
---
Changes from v1:
* Assert VFIOBAR->size and set VFIOBAR->mr to NULL to make the code
more accurate. (Philippe)
* Small reword in the last paragraph of the commit message.
hw/vfio/pci.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index ab6645ba60..bc98791cbb 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1752,9 +1752,11 @@ static void vfio_bars_finalize(VFIOPCIDevice
*vdev)
vfio_bar_quirk_finalize(vdev, i);
vfio_region_finalize(&bar->region);
- if (bar->size) {
+ if (bar->mr) {
+ assert(bar->size);
object_unparent(OBJECT(bar->mr));
g_free(bar->mr);
+ bar->mr = NULL;
}
}
