On 200511 0910, Philippe Mathieu-Daudé wrote: > On 5/11/20 8:19 AM, Philippe Mathieu-Daudé wrote: > > On 5/11/20 6:59 AM, Alexander Bulekov wrote: > > > Hello, > > > While fuzzing, I found an input that triggers an assertion failure in > > > mch_update_pciexbar: > > > > > > #6 0x7f38d387c55a in abort > > > /build/glibc-GwnBeO/glibc-2.30/stdlib/abort.c:79:7 > > > #7 0x55c27e94ffd0 in mch_update_pciexbar hw/pci-host/q35.c:331:9 > > > #8 0x55c27e94db38 in mch_write_config hw/pci-host/q35.c:487:9 > > > #9 0x55c27e9e3f4c in pci_host_config_write_common hw/pci/pci_host.c:81:5 > > > #10 0x55c27e9e5307 in pci_data_write hw/pci/pci_host.c:118:5 > > > #11 0x55c27e9e6601 in pci_host_data_write hw/pci/pci_host.c:165:9 > > > #12 0x55c27ca3b17b in memory_region_write_accessor memory.c:496:5 > > > #13 0x55c27ca3a5e4 in access_with_adjusted_size memory.c:557:18 > > > #14 0x55c27ca38177 in memory_region_dispatch_write memory.c:1488:16 > > > #15 0x55c27c721325 in flatview_write_continue exec.c:3174:23 > > > #16 0x55c27c70994d in flatview_write exec.c:3214:14 > > > #17 0x55c27c709462 in address_space_write exec.c:3305:18 > > > > These lines don't match QEMU v5.0.0.
Right... I'll make sure the stack-trace comes from the same version in the future. > > > > > > I can reproduce it in a qemu 5.0 build using: > > > cat << EOF | ~/Development/qemu/build/i386-softmmu/qemu-system-i386 > > > -M pc-q35-5.0 -display none -nodefaults -nographic -qtest stdio > > > outl 0xcf8 0xf2000060 > > > outl 0xcfc 0x8400056e > > > > The guest shouldn't ask for a reserved bar length (grep for > > MCH_HOST_BRIDGE_PCIEXBAR_LENGTH_RVD). I suppose we should simply report > > it as GUEST_ERROR and ignore it. > > This patch prevent the crash: > > -- >8 -- > diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c > index 2bbc90b28f..2b744aca93 100644 > --- a/hw/pci-host/q35.c > +++ b/hw/pci-host/q35.c > @@ -36,6 +36,7 @@ > #include "qapi/error.h" > #include "qapi/visitor.h" > #include "qemu/module.h" > +#include "qemu/log.h" > > > /**************************************************************************** > * Q35 host > @@ -320,6 +321,9 @@ static void mch_update_pciexbar(MCHPCIState *mch) > addr_mask |= MCH_HOST_BRIDGE_PCIEXBAR_64ADMSK; > break; > case MCH_HOST_BRIDGE_PCIEXBAR_LENGTH_RVD: > + qemu_log_mask(LOG_GUEST_ERROR, "%s: Invalid use of reserved > value\n", > + __func__); > + return; > default: > abort(); > } > --- > > But the real question is what would the real hardware do in this case. > > > > > > EOF > > > > > > I also uploaded the above trace, in case the formatting is broken: > > > > > > curl https://paste.debian.net/plain/1146095 | qemu-system-i386 -M > > > pc-q35-5.0 -display none -nodefaults -nographic -qtest stdio > > > > > > Please let me know if I can provide any further info. > > > > It would help the community if you fill your bug reports with Launchpad, > > so they don't get lost in the high email flow, and we can track/update > > them. See for example: > > https://bugs.launchpad.net/qemu/+bug/1835865 and > > https://lists.gnu.org/archive/html/qemu-devel/2020-03/msg06082.html > > which refers it. OK, I'll use that from now on. Thanks -Alex
