| Message ID | 20240531110343.3800767-1-namcao@linutronix.de (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: Bail out if bus number overflows during scan | expand |
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 1325fbae2f28..03caae76337c 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1382,6 +1382,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev, else next_busnr = max + 1; + if (next_busnr == 256) + goto out; + /* * Prevent assigning a bus number that already exists. * This can happen when a bridge is hot-plugged, so in this
In function pci_scan_bridge_extend(), if the variable next_busnr gets to 256, "child = pci_find_bus()" will return bus 0 (root bus). Consequently, we have a circular PCI topology. The scan will then go in circle until the kernel crashes due to stack overflow. This can be reproduced with: qemu-system-x86_64 -machine pc-q35-2.10 \ -kernel bzImage \ -m 2048 -smp 1 -enable-kvm \ -append "console=ttyS0 root=/dev/sda debug" \ -nographic \ -device pcie-root-port,bus=pcie.0,slot=1,id=rp1,bus-reserve=253 \ -device pcie-root-port,bus=pcie.0,slot=2,id=rp2,bus-reserve=0 \ -device pcie-root-port,bus=pcie.0,slot=3,id=rp3,bus-reserve=0 Check if next_busnr "overflow" and bail out if this is the case. Signed-off-by: Nam Cao <namcao@linutronix.de> Cc: stable@vger.kernel.org # all --- This bug exists since the beginning of git history. So I didn't bother tracing beyond git to see which patch introduced this. --- drivers/pci/probe.c | 3 +++ 1 file changed, 3 insertions(+)