diff options
Diffstat (limited to 'gitlab/issues_text/target_i386/host_missing/accel_missing/810')
| -rw-r--r-- | gitlab/issues_text/target_i386/host_missing/accel_missing/810 | 71 |
1 files changed, 0 insertions, 71 deletions
diff --git a/gitlab/issues_text/target_i386/host_missing/accel_missing/810 b/gitlab/issues_text/target_i386/host_missing/accel_missing/810 deleted file mode 100644 index 12bb57b34..000000000 --- a/gitlab/issues_text/target_i386/host_missing/accel_missing/810 +++ /dev/null @@ -1,71 +0,0 @@ -i386/sev: Crash in pc_system_parse_ovmf_flash caused by bad firmware file -Description of problem: -A specially-crafted flash file can cause the `memcpy()` call in -`pc_system_parse_ovmf_flash` (`hw/i386/pc_sysfw_ovmf.c`) to READ out-of-bounds -memory, because there's no check on the `tot_len` field which is read -from the flash file. In such case, `ptr - tot_len` will point to a -memory location *below* `flash_ptr` (hence the out-of-bounds read). - -This path is only taken when SEV is enabled (which requires -KVM and x86_64). -Steps to reproduce: -1. Create `bad_ovmf.fd` using the following python script: - ``` - from uuid import UUID - OVMF_TABLE_FOOTER_GUID = "96b582de-1fb2-45f7-baea-a366c55a082d" - b = bytearray(4096) - b[4046:4048] = b'\xff\xff' # tot_len field - b[4048:4064] = UUID("{" + OVMF_TABLE_FOOTER_GUID + "}").bytes_le - with open("bad_ovmf.fd", "wb") as f: - f.write(b) - ``` -2. Build QEMU with `--enable-sanitizers` -3. Start QEMU with SEV and the bad flash file: - ``` - qemu-system-x86_64 -enable-kvm -cpu host -machine q35 \ - -drive if=pflash,format=raw,unit=0,file=bad_ovmf.fd,readonly=on \ - -machine confidential-guest-support=sev0 \ - -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1,policy=0x0 - ``` -4. QEMU crashes with: `SUMMARY: AddressSanitizer: stack-buffer-underflow` -Additional information: -Crash example: - -``` -$ sudo build/qemu-system-x86_64 -enable-kvm -cpu host -machine q35 \ - -drive if=pflash,format=raw,unit=0,file=bad_ovmf.fd,readonly=on \ - -machine confidential-guest-support=sev0 \ - -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1,policy=0x0 -==523314==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases! -================================================================= -==523314==ERROR: AddressSanitizer: stack-buffer-underflow on address 0x7f05305fb180 at pc 0x7f0548d89480 bp 0x7ffed44a1980 sp 0x7ffed44a1128 -READ of size 65517 at 0x7f05305fb180 thread T0 - #0 0x7f0548d8947f (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x9b47f) - #1 0x556127c3331e in memcpy /usr/include/x86_64-linux-gnu/bits/string_fortified.h:34 - #2 0x556127c3331e in pc_system_parse_ovmf_flash ../hw/i386/pc_sysfw_ovmf.c:82 - #3 0x556127c21a0c in pc_system_flash_map ../hw/i386/pc_sysfw.c:203 - #4 0x556127c21a0c in pc_system_firmware_init ../hw/i386/pc_sysfw.c:258 - #5 0x556127c1ddd9 in pc_memory_init ../hw/i386/pc.c:902 - #6 0x556127bdc387 in pc_q35_init ../hw/i386/pc_q35.c:207 - #7 0x5561273bfdd6 in machine_run_board_init ../hw/core/machine.c:1181 - #8 0x556127f77de1 in qemu_init_board ../softmmu/vl.c:2652 - #9 0x556127f77de1 in qmp_x_exit_preconfig ../softmmu/vl.c:2740 - #10 0x556127f7f24d in qemu_init ../softmmu/vl.c:3775 - #11 0x556126f947ac in main ../softmmu/main.c:49 - #12 0x7f05470e80b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2) - #13 0x556126fa639d in _start (/home/dmurik/git/qemu/build/qemu-system-x86_64+0x2a5739d) - -Address 0x7f05305fb180 is located in stack of thread T3 at offset 0 in frame - #0 0x556128a96f1f in qemu_sem_timedwait ../util/qemu-thread-posix.c:293 - - - This frame has 1 object(s): - [32, 48) 'ts' (line 295) <== Memory access at offset 0 partially underflows this variable -HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork - (longjmp and C++ exceptions *are* supported) -Thread T3 created by T0 here: - #0 0x7f0548d28805 in pthread_create (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x3a805) - #1 0x556128a97ecf in qemu_thread_create ../util/qemu-thread-posix.c:596 - -SUMMARY: AddressSanitizer: stack-buffer-underflow (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x9b47f) -``` |