LoongArch: Don't crash in stack_top() for tasks without vDSO
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: 803b0fc5c3
("LoongArch: Add process management")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
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2ed119aef6
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@ -293,6 +293,7 @@ unsigned long stack_top(void)
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{
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unsigned long top = TASK_SIZE & PAGE_MASK;
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if (current->thread.vdso) {
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/* Space for the VDSO & data page */
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top -= PAGE_ALIGN(current->thread.vdso->size);
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top -= VVAR_SIZE;
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@ -300,6 +301,7 @@ unsigned long stack_top(void)
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/* Space to randomize the VDSO base */
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if (current->flags & PF_RANDOMIZE)
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top -= VDSO_RANDOMIZE_SIZE;
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}
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return top;
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}
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