From: Marco Elver elver@google.com
[ Upstream commit 09c6304e38e440b93a9ebf3f3cf75cd6cb529f91 ]
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 FORTIFY_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: | 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.
Link: https://lkml.kernel.org/r/20220124160744.1244685-1-elver@google.com Signed-off-by: Marco Elver elver@google.com Reported-by: Nico Pache npache@redhat.com Reviewed-by: Nico Pache npache@redhat.com Reviewed-by: Andrey Konovalov andreyknvl@gmail.com Reviewed-by: Kees Cook keescook@chromium.org Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Brendan Higgins brendanhiggins@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- lib/test_kasan.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 0643573f86862..2ef2948261bf8 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); @@ -869,6 +872,7 @@ 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)); @@ -895,6 +899,7 @@ 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));