Re: [PULL 0/5] 9p queue 2022-02-10

[Christian Schoenebeck]

On Sonntag, 13. Februar 2022 21:33:10 CET Peter Maydell wrote:
> On Thu, 10 Feb 2022 at 11:33, Christian Schoenebeck
> 
> <qemu_oss@crudebyte.com> wrote:
> > The following changes since commit 0a301624c2f4ced3331ffd5bce85b4274fe132af:
> >   Merge remote-tracking branch
> >   'remotes/pmaydell/tags/pull-target-arm-20220208' into staging
> >   (2022-02-08 11:40:08 +0000)> 
> > are available in the Git repository at:
> >   https://github.com/cschoenebeck/qemu.git tags/pull-9p-20220210
> > 
> > for you to fetch changes up to de19c79dad6a2cad54ae04ce754d47c07bf9bc93:
> >   9pfs: Fix segfault in do_readdir_many caused by struct dirent overread
> >   (2022-02-10 11:56:01 +0100)> 
> > ----------------------------------------------------------------
> > 9pfs: fixes and cleanup
> > 
> > * Fifth patch fixes a 9pfs server crash that happened on some systems due
> > 
> >   to incorrect (system dependant) handling of struct dirent size.
> > 
> > * Tests: Second patch fixes a test error that happened on some systems due
> > 
> >   mkdir() being called twice for creating the test directory for the 9p
> >   'local' tests.
> > 
> > * Tests: Third patch fixes a memory leak.
> > 
> > * Tests: The remaining two patches are code cleanup.
> > 
> > ----------------------------------------------------------------
> 
> Hi; this fails CI for the build-oss-fuzz job, which finds
> a heap-buffer-overflow:
> https://gitlab.com/qemu-project/qemu/-/jobs/2087610013

So this is about the 'dirent' patch:
https://github.com/cschoenebeck/qemu/commit/de19c79dad6a2cad54ae04ce754d47c07bf9bc93

In conjunction with the 9p fuzzing tests:
https://wiki.qemu.org/Documentation/9p#Fuzzing

I first thought it might be a false positive due to the unorthodox handling of
dirent duplication by that patch, but from the ASan output below I am not
really sure about that.

Is there a way to get the content of local variables?

Would it be possible that the following issue (g_memdup vs. g_memdup2) might
apply here?
https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-now/5538

Best regards,
Christian Schoenebeck

> 
> 8/152 qemu:qtest+qtest-i386 / qtest-i386/qos-test ERROR 66.74s killed
> by signal 6 SIGABRT
> 
> >>> QTEST_QEMU_BINARY=./qemu-system-i386
> >>> QTEST_QEMU_STORAGE_DAEMON_BINARY=./storage-daemon/qemu-storage-daemon
> >>> MALLOC_PERTURB_=120
> >>> G_TEST_DBUS_DAEMON=/builds/qemu-project/qemu/tests/dbus-vmstate-daemon.
> >>> sh QTEST_QEMU_IMG=./qemu-img
> >>> /builds/qemu-project/qemu/build-oss-fuzz/tests/qtest/qos-test --tap -k
> ――――――――――――――――――――――――――――――――――――― ✀
> ――――――――――――――――――――――――――――――――――――― Listing only the last 100 lines from
> a long log.
> For details see https://github.com/google/sanitizers/issues/189
> ==7270==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7270==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7ffc79fb0000; bottom 0x7ff908ffd000; size:
> 0x000370fb3000 (14780411904)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> ==7276==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7276==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7fff7e4a8000; bottom 0x7fd6363fd000; size:
> 0x0029480ab000 (177302319104)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> ==7282==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7282==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7ffee6e7f000; bottom 0x7f32fb5fd000; size:
> 0x00cbeb882000 (875829927936)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> ==7288==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7288==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7ffc6118e000; bottom 0x7f6391cfd000; size:
> 0x0098cf491000 (656312700928)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> ==7294==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7294==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7ffef665d000; bottom 0x7f69dc8fd000; size:
> 0x009519d60000 (640383582208)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> ==7300==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7300==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7ffe33db0000; bottom 0x7f01421fd000; size:
> 0x00fcf1bb3000 (1086387335168)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> ==7306==WARNING: ASan doesn't fully support makecontext/swapcontext
> functions and may produce false positives in some cases!
> ==7306==WARNING: ASan is ignoring requested __asan_handle_no_return:
> stack type: default top: 0x7ffebd618000; bottom 0x7ff1179fd000; size:
> 0x000da5c1b000 (58615508992)
> False positive error reports may follow
> For details see https://github.com/google/sanitizers/issues/189
> =================================================================
> ==7306==ERROR: AddressSanitizer: heap-buffer-overflow on address
> 0x612000030768 at pc 0x562351066c74 bp 0x7ff1078c3a90 sp
> 0x7ff1078c3240
> READ of size 48830 at 0x612000030768 thread T4
> #0 0x562351066c73 in __interceptor_memcpy.part.0 asan_interceptors.cpp.o
> #1 0x7ff1290d443f in g_memdup (/lib64/libglib-2.0.so.0+0x6e43f)
> #2 0x56235134537a in do_readdir_many
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/codir.c:146:19
> #3 0x56235134537a in v9fs_co_readdir_many
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/codir.c:225:5
> #4 0x56235132d626 in v9fs_do_readdir
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/9p.c:2430:13
> #5 0x56235132d626 in v9fs_readdir
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/9p.c:2543:13
> #6 0x56235257101e in coroutine_trampoline
> /builds/qemu-project/qemu/build-oss-fuzz/../util/coroutine-ucontext.c:173:9
> #7 0x7ff126e0e84f (/lib64/libc.so.6+0x5784f)
> 0x612000030768 is located 0 bytes to the right of 296-byte region
> [0x612000030640,0x612000030768)
> allocated by thread T4 here:
> #0 0x5623510a4e47 in malloc
> (/builds/qemu-project/qemu/build-oss-fuzz/qemu-system-i386+0x1146e47)
> #1 0x7ff1290c03d8 in g_malloc (/lib64/libglib-2.0.so.0+0x5a3d8)
> #2 0x56235131e659 in synth_opendir
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/9p-synth.c:185:18
> #3 0x5623513462f5 in v9fs_co_opendir
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/codir.c:321:5
> #4 0x5623513257d7 in v9fs_open
> /builds/qemu-project/qemu/build-oss-fuzz/../hw/9pfs/9p.c:1959:15
> #5 0x56235257101e in coroutine_trampoline
> /builds/qemu-project/qemu/build-oss-fuzz/../util/coroutine-ucontext.c:173:9
> #6 0x7ff126e0e84f (/lib64/libc.so.6+0x5784f)
> Thread T4 created by T0 here:
> #0 0x562351015926 in pthread_create
> (/builds/qemu-project/qemu/build-oss-fuzz/qemu-system-i386+0x10b7926)
> #1 0x5623525351ea in qemu_thread_create
> /builds/qemu-project/qemu/build-oss-fuzz/../util/qemu-thread-posix.c:596:11
> #2 0x5623525a4588 in do_spawn_thread
> /builds/qemu-project/qemu/build-oss-fuzz/../util/thread-pool.c:134:5
> #3 0x5623525a4588 in spawn_thread_bh_fn
> /builds/qemu-project/qemu/build-oss-fuzz/../util/thread-pool.c:142:5
> #4 0x562352569814 in aio_bh_call
> /builds/qemu-project/qemu/build-oss-fuzz/../util/async.c:141:5
> #5 0x562352569814 in aio_bh_poll
> /builds/qemu-project/qemu/build-oss-fuzz/../util/async.c:169:13
> #6 0x5623525248cc in aio_dispatch
> /builds/qemu-project/qemu/build-oss-fuzz/../util/aio-posix.c:415:5
> #7 0x56235256c34c in aio_ctx_dispatch
> /builds/qemu-project/qemu/build-oss-fuzz/../util/async.c:311:5
> #8 0x7ff1290bb05e in g_main_context_dispatch
> (/lib64/libglib-2.0.so.0+0x5505e) SUMMARY: AddressSanitizer:
> heap-buffer-overflow
> asan_interceptors.cpp.o in __interceptor_memcpy.part.0
> Shadow bytes around the buggy address:
> 0x0c247fffe090: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
> 0x0c247fffe0a0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
> 0x0c247fffe0b0: fd fd fd fd fd fd fd fd fd fd fd fd fd fa fa fa
> 0x0c247fffe0c0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
> 0x0c247fffe0d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> =>0x0c247fffe0e0: 00 00 00 00 00 00 00 00 00 00 00 00 00[fa]fa fa
> 0x0c247fffe0f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> 0x0c247fffe100: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> 0x0c247fffe110: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> 0x0c247fffe120: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> 0x0c247fffe130: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> Shadow byte legend (one shadow byte represents 8 application bytes):
> Addressable: 00
> Partially addressable: 01 02 03 04 05 06 07
> Heap left redzone: fa
> Freed heap region: fd
> Stack left redzone: f1
> Stack mid redzone: f2
> Stack right redzone: f3
> Stack after return: f5
> Stack use after scope: f8
> Global redzone: f9
> Global init order: f6
> Poisoned by user: f7
> Container overflow: fc
> Array cookie: ac
> Intra object redzone: bb
> ASan internal: fe
> Left alloca redzone: ca
> Right alloca redzone: cb
> ==7306==ABORTING
> 
> 
> thanks
> -- PMM