On 1/24/22 11:07, Marco Elver wrote: > With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform > dynamic checks using __builtin_object_size(ptr), which when failed will > panic the kernel. > > Because the KASAN test deliberately performs out-of-bounds operations, > the kernel panics with FORITY_SOURCE, for example: > > | kernel BUG at lib/string_helpers.c:910! > | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI > | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G B 5.16.0-rc3+ #3 > | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 > | RIP: 0010:fortify_panic+0x19/0x1b > | ... > | Call Trace: > | <TASK> > | kmalloc_oob_in_memset.cold+0x16/0x16 > | ... > > Fix it by also hiding `ptr` from the optimizer, which will ensure that > __builtin_object_size() does not return a valid size, preventing > fortified string functions from panicking. > > Reported-by: Nico Pache <npache@xxxxxxxxxx> > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Looks good! Thanks for posting this Marco :) Reviewed-by: Nico Pache <npache@xxxxxxxxxx> > --- > lib/test_kasan.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/lib/test_kasan.c b/lib/test_kasan.c > index 847cdbefab46..26a5c9007653 100644 > --- a/lib/test_kasan.c > +++ b/lib/test_kasan.c > @@ -492,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test) > ptr = kmalloc(size, GFP_KERNEL); > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > + OPTIMIZER_HIDE_VAR(ptr); > OPTIMIZER_HIDE_VAR(size); > KUNIT_EXPECT_KASAN_FAIL(test, > memset(ptr, 0, size + KASAN_GRANULE_SIZE)); > @@ -515,6 +516,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test) > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > memset((char *)ptr, 0, 64); > + OPTIMIZER_HIDE_VAR(ptr); > OPTIMIZER_HIDE_VAR(invalid_size); > KUNIT_EXPECT_KASAN_FAIL(test, > memmove((char *)ptr, (char *)ptr + 4, invalid_size)); > @@ -531,6 +533,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test) > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > memset((char *)ptr, 0, 64); > + OPTIMIZER_HIDE_VAR(ptr); > KUNIT_EXPECT_KASAN_FAIL(test, > memmove((char *)ptr, (char *)ptr + 4, invalid_size)); > kfree(ptr); > @@ -893,6 +896,7 @@ static void kasan_memchr(struct kunit *test) > ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO); > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > + OPTIMIZER_HIDE_VAR(ptr); > OPTIMIZER_HIDE_VAR(size); > KUNIT_EXPECT_KASAN_FAIL(test, > kasan_ptr_result = memchr(ptr, '1', size + 1)); > @@ -919,6 +923,7 @@ static void kasan_memcmp(struct kunit *test) > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > memset(arr, 0, sizeof(arr)); > > + OPTIMIZER_HIDE_VAR(ptr); > OPTIMIZER_HIDE_VAR(size); > KUNIT_EXPECT_KASAN_FAIL(test, > kasan_int_result = memcmp(ptr, arr, size+1)); >
