Re: [RFC PATCH] scripts/lsan-suppressions: Add a LeakSanitizer suppressions file

[Peter Maydell]

On Mon, 19 Aug 2024 at 18:07, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> Add a LeakSanitizer suppressions file that documents and suppresses
> known false-positive leaks in either QEMU or its dependencies.
> To use it you'll need to set
>   LSAN_OPTIONS="suppressions=/path/to/scripts/lsan-suppressions.txt"
> when running a QEMU built with the leak-sanitizer.
>
> The first and currently only entry is for a deliberate leak in glib's
> g_set_user_dirs() that otherwise causes false positive leak reports
> in the qga-ssh-test because of its use of G_TEST_OPTION_ISOLATE_DIRS:
>
> Direct leak of 321 byte(s) in 5 object(s) allocated from:
>     #0 0x5555dd8abd1e in __interceptor_malloc 
> (/mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/asan/qga/qga-ssh-test+0x19cd1e)
>  (BuildId: 7991a166007e8206c51bee401722a8335e7990bb)
>     #1 0x7fb5bc724738 in g_malloc debian/build/deb/../../../glib/gmem.c:128:13
>     #2 0x7fb5bc739583 in g_strdup 
> debian/build/deb/../../../glib/gstrfuncs.c:361:17
>     #3 0x7fb5bc757a29 in set_str_if_different 
> debian/build/deb/../../../glib/gutils.c:1659:21
>     #4 0x7fb5bc757a29 in set_str_if_different 
> debian/build/deb/../../../glib/gutils.c:1647:1
>     #5 0x7fb5bc757a29 in g_set_user_dirs 
> debian/build/deb/../../../glib/gutils.c:1743:9
>     #6 0x7fb5bc743d78 in test_do_isolate_dirs 
> debian/build/deb/../../../glib/gtestutils.c:1486:3
>     #7 0x7fb5bc743d78 in test_case_run 
> debian/build/deb/../../../glib/gtestutils.c:2917:16
>     #8 0x7fb5bc743d78 in g_test_run_suite_internal 
> debian/build/deb/../../../glib/gtestutils.c:3018:16
>     #9 0x7fb5bc74380a in g_test_run_suite_internal 
> debian/build/deb/../../../glib/gtestutils.c:3035:18
>     #10 0x7fb5bc74380a in g_test_run_suite_internal 
> debian/build/deb/../../../glib/gtestutils.c:3035:18
>     #11 0x7fb5bc743fe9 in g_test_run_suite 
> debian/build/deb/../../../glib/gtestutils.c:3112:13
>     #12 0x7fb5bc744055 in g_test_run 
> debian/build/deb/../../../glib/gtestutils.c:2231:7
>     #13 0x7fb5bc744055 in g_test_run 
> debian/build/deb/../../../glib/gtestutils.c:2218:1
>     #14 0x5555dd9293b1 in main qga/commands-posix-ssh.c:439:12
>     #15 0x7fb5bc3dfd8f in __libc_start_call_main 
> csu/../sysdeps/nptl/libc_start_call_main.h:58:16
>     #16 0x7fb5bc3dfe3f in __libc_start_main csu/../csu/libc-start.c:392:3
>     #17 0x5555dd828ed4 in _start 
> (/mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/asan/qga/qga-ssh-test+0x119ed4)
>  (BuildId: 7991a166007e8206c51bee401722a8335e7990bb)
>
> (Strictly speaking, this is a genuine leak, it's just a deliberate
> one by glib; they document it in their valgrind-format suppression
> file upstream.)
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> Does this seem like a good idea?  It gives us a place to document
> things like this and to suppress them so we could in theory get a
> complete clean 'make check' run with the leak sanitizer on.  It might
> be nice if there was an easy way to enable all our "recommended
> sanitizer settings" (ASAN_OPTIONS="fast_unwind_on_malloc=0 is
> pretty much required to get useful backtraces, for instance), but
> I'm not sure there's a neat way to do that.

On the "no" end of the argument: it looks like from glib 2.79
or thereabouts there was support added to glib to make it
dynamically detect whether it's running in a binary that was
built with LSan and explicitly tell lsan to ignore these
deliberate leaks. That fix is less than a year old, though,
and at least my dev machine is still running 2.72.

https://github.com/GNOME/glib/commit/fb58d55187dfe1565d10c0c0ffdbaa85376cf0b8

-- PMM