Messages in this thread | | | Date | Fri, 19 Jul 2019 10:03:44 -0700 | From | Sean Christopherson <> | Subject | [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace on i386 |
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The generic vDSO implementation, starting with commit
7ac870747988 ("x86/vdso: Switch to generic vDSO implementation")
breaks seccomp-enabled userspace on 32-bit x86 (i386) kernels. Prior to the generic implementation, the x86 vDSO used identical code for both x86_64 and i386 kernels, which worked because it did all calcuations using structs with naturally sized variables, i.e. didn't use __kernel_timespec.
The generic vDSO does its internal calculations using __kernel_timespec, which in turn requires the i386 fallback syscall to use the 64-bit variation, __NR_clock_gettime64.
Using __NR_clock_gettime64 instead of __NR_clock_gettime breaks userspace applications that use seccomp filtering to block syscalls, as applications are completely unaware of the newly added of __NR_clock_gettime64, e.g. sshd gets zapped on syscall(403) when attempting to ssh into the system.
I can fudge around the issue easily enough, but I have no idea how to fix this properly without duplicating __cvdso_clock_gettime, do_hres, etc..., especially now that the i386 vDSO exposes __vdso_clock_gettime64().
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