| Message ID | 20230704133927.24677-1-avihaih@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] vfio: Fix null pointer dereference bug in vfio_bars_finalize() | expand |
On 4/7/23 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(). > > Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") > Signed-off-by: Avihai Horon <avihaih@nvidia.com> > --- > > 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(-) Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
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 ? > > Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") > Signed-off-by: Avihai Horon <avihaih@nvidia.com> Reviewed-by: Cédric Le Goater <clg@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; > } > } >
On 04/07/2023 18:54, Cédric Le Goater wrote: > External email: Use caution opening links or attachments > > > 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 <avihaih@nvidia.com> > > > Reviewed-by: Cédric Le Goater <clg@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; >> } >> } >> >
On Tue, 4 Jul 2023 16:39:27 +0300 Avihai Horon <avihaih@nvidia.com> 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(). > > Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") > Signed-off-by: Avihai Horon <avihaih@nvidia.com> > --- > > 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; > } > } > Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
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; } }
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(). Fixes: 89d5202edc50 ("vfio/pci: Allow relocating MSI-X MMIO") Signed-off-by: Avihai Horon <avihaih@nvidia.com> --- 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(-)