| Message ID | 20230703163953.18526-1-avihaih@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfio: Fix null pointer dereference bug in vfio_bars_finalize() | expand |
On 3/7/23 18:39, 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 unconditionally and thus we get a null > pointer dereference. > > Fix it by checking VFIOBAR->mr in vfio_bars_finalize(). > > Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") > Signed-off-by: Avihai Horon <avihaih@nvidia.com> > --- > hw/vfio/pci.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c > index ab6645ba60..95e077082b 100644 > --- a/hw/vfio/pci.c > +++ b/hw/vfio/pci.c > @@ -1752,7 +1752,7 @@ static void vfio_bars_finalize(VFIOPCIDevice *vdev) > > vfio_bar_quirk_finalize(vdev, i); > vfio_region_finalize(&bar->region); > - if (bar->size) { > + if (bar->size && bar->mr) { > object_unparent(OBJECT(bar->mr)); > g_free(bar->mr); > } What about: if (bar->mr) { assert(bar->size); object_unparent(OBJECT(bar->mr)); g_free(bar->mr); bar->mr = NULL; } ?
On 03/07/2023 19:56, Philippe Mathieu-Daudé wrote: > External email: Use caution opening links or attachments > > > On 3/7/23 18:39, 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 unconditionally and thus we get a null >> pointer dereference. >> >> Fix it by checking VFIOBAR->mr in vfio_bars_finalize(). >> >> Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") >> Signed-off-by: Avihai Horon <avihaih@nvidia.com> >> --- >> hw/vfio/pci.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c >> index ab6645ba60..95e077082b 100644 >> --- a/hw/vfio/pci.c >> +++ b/hw/vfio/pci.c >> @@ -1752,7 +1752,7 @@ static void vfio_bars_finalize(VFIOPCIDevice >> *vdev) >> >> vfio_bar_quirk_finalize(vdev, i); >> vfio_region_finalize(&bar->region); >> - if (bar->size) { >> + if (bar->size && bar->mr) { >> object_unparent(OBJECT(bar->mr)); >> g_free(bar->mr); >> } > > What about: > > if (bar->mr) { > assert(bar->size); > object_unparent(OBJECT(bar->mr)); > g_free(bar->mr); > bar->mr = NULL; > } > > ? Nice touch, it's indeed more accurate. Will change and post v2. Thanks!
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c index ab6645ba60..95e077082b 100644 --- a/hw/vfio/pci.c +++ b/hw/vfio/pci.c @@ -1752,7 +1752,7 @@ static void vfio_bars_finalize(VFIOPCIDevice *vdev) vfio_bar_quirk_finalize(vdev, i); vfio_region_finalize(&bar->region); - if (bar->size) { + if (bar->size && bar->mr) { object_unparent(OBJECT(bar->mr)); g_free(bar->mr); }
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 unconditionally and thus we get a null pointer dereference. Fix it by checking VFIOBAR->mr in vfio_bars_finalize(). Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") Signed-off-by: Avihai Horon <avihaih@nvidia.com> --- hw/vfio/pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)