On Tue, Oct 15, 2024 at 2:14 PM Thomas Weißschuh thomas.weissschuh@linutronix.de wrote:
Hi Huacai,
On Tue, Oct 15, 2024 at 10:15:39AM +0800, Huacai Chen wrote:
I can take this patch to the loongarch tree, but I think others should get upstream via kselftests tree?
Yes, sounds good. Could you take a look at patches 2 and 4, too?
Bibo is more familiar with those, so +CC Bibo. This one is queued in the loongarch tree. Thanks.
Huacai
Thanks, Thomas
On Mon, Oct 14, 2024 at 7:36 PM Thomas Weißschuh thomas.weissschuh@linutronix.de wrote:
Not all tasks have a vDSO mapped, for example kthreads never do. If such a task ever ends up calling stack_top(), it will derefence the NULL vdso pointer and crash.
This can for example happen when using kunit:
[<9000000000203874>] stack_top+0x58/0xa8 [<90000000002956cc>] arch_pick_mmap_layout+0x164/0x220 [<90000000003c284c>] kunit_vm_mmap_init+0x108/0x12c [<90000000003c1fbc>] __kunit_add_resource+0x38/0x8c [<90000000003c2704>] kunit_vm_mmap+0x88/0xc8 [<9000000000410b14>] usercopy_test_init+0xbc/0x25c [<90000000003c1db4>] kunit_try_run_case+0x5c/0x184 [<90000000003c3d54>] kunit_generic_run_threadfn_adapter+0x24/0x48 [<900000000022e4bc>] kthread+0xc8/0xd4 [<9000000000200ce8>] ret_from_kernel_thread+0xc/0xa4Fixes: 803b0fc5c3f2 ("LoongArch: Add process management") Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de
arch/loongarch/kernel/process.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c index f2ff8b5d591e4fd638109d2c98d75543c01a112c..6e58f65455c7ca3eae2e88ed852c8655a6701e5c 100644 --- a/arch/loongarch/kernel/process.c +++ b/arch/loongarch/kernel/process.c @@ -293,13 +293,15 @@ unsigned long stack_top(void) { unsigned long top = TASK_SIZE & PAGE_MASK;
/* Space for the VDSO & data page */top -= PAGE_ALIGN(current->thread.vdso->size);top -= VVAR_SIZE;/* Space to randomize the VDSO base */if (current->flags & PF_RANDOMIZE)top -= VDSO_RANDOMIZE_SIZE;
if (current->thread.vdso) {/* Space for the VDSO & data page */top -= PAGE_ALIGN(current->thread.vdso->size);top -= VVAR_SIZE;/* Space to randomize the VDSO base */if (current->flags & PF_RANDOMIZE)top -= VDSO_RANDOMIZE_SIZE;} return top;}
-- 2.47.0