6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
[ Upstream commit 134475a9ab8487527238d270639a8cb74c10aab2 ]
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/0xa4
Fixes: 803b0fc5c3f2 ("LoongArch: Add process management")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 51176e5ecee59..4561bc81c0639 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -271,13 +271,15 @@ 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;
}
--
2.43.0
