diff options
| author | Qiang Liu <cyruscyliu@gmail.com> | 2022-08-26 13:15:56 +0800 |
|---|---|---|
| committer | Gerd Hoffmann <kraxel@redhat.com> | 2022-09-23 14:38:27 +0200 |
| commit | d8c2e6f2f6d29ccb766197181eb1c65c1d46b3a4 (patch) | |
| tree | bb978712ff27d5af6bae8828bd2652c26b785d03 /hw | |
| parent | 0b33bb394d0d02918679064caa11ef59e5ff3924 (diff) | |
hcd-ohci: Drop ohci_service_iso_td() if ed->head & OHCI_DPTR_MASK is zero
An abort happens in ohci_frame_boundary() when ohci->done is 0 [1].
``` c
static void ohci_frame_boundary(void *opaque)
{
// ...
if (ohci->done_count == 0 && !(ohci->intr_status & OHCI_INTR_WD)) {
if (!ohci->done)
abort(); <----------------------------------------- [1]
```
This was reported in https://bugs.launchpad.net/qemu/+bug/1911216/,
https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg03613.html, and
https://gitlab.com/qemu-project/qemu/-/issues/545. I can still reproduce it with
the latest QEMU.
This happends due to crafted ED with putting ISO_TD at physical address 0.
Suppose ed->head & OHCI_DPTR_MASK is 0 [2], and we memset 0 to the phyiscal
memory from 0 to sizeof(ohci_iso_td). Then, starting_frame [3] and frame_count
[4] are both 0. As we can control the value of ohci->frame_number (0 to 0x1f,
suppose 1), we then control the value of relative_frame_number to be 1 [6]. The
control flow goes to [7] where ohci->done is 0. Have returned from
ohci_service_iso_td(), ohci_frame_boundary() will abort() [1].
``` c
static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed)
{
// ...
addr = ed->head & OHCI_DPTR_MASK; // <--------------------- [2]
if (ohci_read_iso_td(ohci, addr, &iso_td)) { // <-------- [3]
// ...
starting_frame = OHCI_BM(iso_td.flags, TD_SF); // <-------- [4]
frame_count = OHCI_BM(iso_td.flags, TD_FC); // <-------- [5]
relative_frame_number = USUB(ohci->frame_number, starting_frame);
// <-------- [6]
if (relative_frame_number < 0) {
return 1;
} else if (relative_frame_number > frame_count) {
// ...
ohci->done = addr; // <-------- [7]
// ...
}
```
As only (afaik) a guest root user can manipulate ED, TD and the physical memory,
this assertion failure is not a security bug.
The idea to fix this issue is to drop ohci_service_iso_td() if ed->head &
OHCI_DPTR_MASK is 0, which is similar to the drop operation for
ohci_service_ed_list() when head is 0. Probably, a similar issue is in
ohci_service_td(). I drop ohci_service_td() if ed->head & OHCI_DPTR_MASK is 0.
Fixes: 7bfe577702 ("OHCI USB isochronous transfers support (Arnon Gilboa)")
Reported-by: Gaoning Pan <pgn@zju.edu.cn>
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Reported-by: Qiang Liu <cyruscyliu@gmail.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/545
Buglink: https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg03613.html
Buglink: https://bugs.launchpad.net/qemu/+bug/1911216
Signed-off-by: Qiang Liu <cyruscyliu@gmail.com>
Message-Id: <20220826051557.119570-1-cyruscyliu@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/usb/hcd-ohci.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c index 895b29fb86..72bdde9261 100644 --- a/hw/usb/hcd-ohci.c +++ b/hw/usb/hcd-ohci.c @@ -571,6 +571,11 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed) addr = ed->head & OHCI_DPTR_MASK; + if (addr == 0) { + ohci_die(ohci); + return 1; + } + if (ohci_read_iso_td(ohci, addr, &iso_td)) { trace_usb_ohci_iso_td_read_failed(addr); ohci_die(ohci); @@ -858,6 +863,11 @@ static int ohci_service_td(OHCIState *ohci, struct ohci_ed *ed) int completion; addr = ed->head & OHCI_DPTR_MASK; + if (addr == 0) { + ohci_die(ohci); + return 1; + } + /* See if this TD has already been submitted to the device. */ completion = (addr == ohci->async_td); if (completion && !ohci->async_complete) { |