On Wed, 25 Feb 2026 at 00:24, Kees Cook <[email protected]> wrote: > > The call to kmalloc_obj(observed.lines) returns "char (*)[3][512]", > a pointer to the whole 2D array. But "expect" wants to be "char (*)[512]", > the decayed pointer type, as if it were observed.lines itself (though > without the "3" bounds). This produces the following build error: > > ../kernel/kcsan/kcsan_test.c: In function '__report_matches': > ../kernel/kcsan/kcsan_test.c:171:16: error: assignment to 'char (*)[512]' > from incompatible pointer type 'char (*)[3][512]' > [-Wincompatible-pointer-types] > 171 | expect = kmalloc_obj(observed.lines); > | ^ > > Instead of changing the "expect" type to "char (*)[3][512]" and > requiring a dereference at each use (e.g. "(expect*)[0]"), just > explicitly cast the return to the desired type. > > Tested with: > > $ ./tools/testing/kunit/kunit.py run \ > --kconfig_add CONFIG_DEBUG_KERNEL=y \ > --kconfig_add CONFIG_KCSAN=y \ > --kconfig_add CONFIG_KCSAN_KUNIT_TEST=y \ > --arch=x86_64 --qemu_args '-smp 2' kcsan > > Reported-by: Nathan Chancellor <[email protected]> > Fixes: 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for > non-scalar types") > Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Marco Elver <[email protected]> I'm assuming you'll take it through your tree. Thanks! > --- > Cc: Marco Elver <[email protected]> > Cc: Dmitry Vyukov <[email protected]> > Cc: <[email protected]> > --- > kernel/kcsan/kcsan_test.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c > index 79e655ea4ca1..ae758150ccb9 100644 > --- a/kernel/kcsan/kcsan_test.c > +++ b/kernel/kcsan/kcsan_test.c > @@ -168,7 +168,7 @@ static bool __report_matches(const struct expect_report > *r) > if (!report_available()) > return false; > > - expect = kmalloc_obj(observed.lines); > + expect = (typeof(expect))kmalloc_obj(observed.lines); > if (WARN_ON(!expect)) > return false; > > -- > 2.34.1 >
