From: Thomas Weißschuh thomas.weissschuh@linutronix.de

stable inclusion from stable-v6.6.58 commit a94c197d4d749954dfaa37e907fcc8c04e4aad7e category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IB2BWS CVE: CVE-2024-50133

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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[ 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@linutronix.de Signed-off-by: Huacai Chen chenhuacai@loongson.cn Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Lin Yujun linyujun809@huawei.com --- 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 4bdbdc52b2c3..4fc999e17488 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; }