On Tue, Jan 09, 2018 at 06:15:27AM -0800, sawlani@xxxxxxxxxx wrote: > From: Pradeep Sawlani <sawlani@xxxxxxxxxx> > > commit e39d200fa5bf5b94a0948db0dae44c1b73b84a56 upstream. > > Reported by syzkaller: > > BUG: KASAN: stack-out-of-bounds in write_mmio+0x11e/0x270 [kvm] > Read of size 8 at addr ffff8803259df7f8 by task syz-executor/32298 > > CPU: 6 PID: 32298 Comm: syz-executor Tainted: G OE 4.15.0-rc2+ #18 > Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016 > Call Trace: > dump_stack+0xab/0xe1 > print_address_description+0x6b/0x290 > kasan_report+0x28a/0x370 > write_mmio+0x11e/0x270 [kvm] > emulator_read_write_onepage+0x311/0x600 [kvm] > emulator_read_write+0xef/0x240 [kvm] > emulator_fix_hypercall+0x105/0x150 [kvm] > em_hypercall+0x2b/0x80 [kvm] > x86_emulate_insn+0x2b1/0x1640 [kvm] > x86_emulate_instruction+0x39a/0xb90 [kvm] > handle_exception+0x1b4/0x4d0 [kvm_intel] > vcpu_enter_guest+0x15a0/0x2640 [kvm] > kvm_arch_vcpu_ioctl_run+0x549/0x7d0 [kvm] > kvm_vcpu_ioctl+0x479/0x880 [kvm] > do_vfs_ioctl+0x142/0x9a0 > SyS_ioctl+0x74/0x80 > entry_SYSCALL_64_fastpath+0x23/0x9a > > The path of patched vmmcall will patch 3 bytes opcode 0F 01 C1(vmcall) > to the guest memory, however, write_mmio tracepoint always prints 8 bytes > through *(u64 *)val since kvm splits the mmio access into 8 bytes. This > leaks 5 bytes from the kernel stack (CVE-2017-17741). This patch fixes > it by just accessing the bytes which we operate on. > > Before patch: > > syz-executor-5567 [007] .... 51370.561696: kvm_mmio: mmio write len 3 gpa 0x10 val 0x1ffff10077c1010f > > After patch: > > syz-executor-13416 [002] .... 51302.299573: kvm_mmio: mmio write len 3 gpa 0x10 val 0xc1010f > > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx> > Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx> > Tested-by: Marc Zyngier <marc.zyngier@xxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx> > Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > [bwh: Backported to 4.4: > -Adjust filename] > Signed-off-by: Pradeep Sawlani <sawlani@xxxxxxxxxx> What kernel(s) do you want this applied to? and who is "bwh" here? thanks, greg k-h