LoongArch: Don't crash in stack_top() for tasks without vDSO

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SUSE CVE-2009-4271

The Linux kernel 2.6.9 through 2.6.17 on the x8664 and amd64 platforms allows local users to cause a denial of service panic via a 32-bit application that calls mprotect on its Virtual Dynamic Shared Object VDSO page and then triggers a segmentation fault...

kernel: ASLR bruteforce possible for vdso library

An information leak flaw was found in the way the Linux kernel's Virtual Dynamic Shared Object vDSO implementation performed address randomization. A local, unprivileged user could use this flaw to leak kernel memory addresses to user-space...

kernel: missing boundary checks in syscall/syscall32_nopage()

Tavis Ormandy reported missing boundary checks in the Virtual Dynamic Shared Objects vDSO implementation. This could allow a local unprivileged user to cause a denial of service or privilege escalation. CVE-2008-3527, Important...