From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace on i386
Date: Fri, 19 Jul 2019 10:03:44 -0700 [thread overview]
Message-ID: <20190719170343.GA13680@linux.intel.com> (raw)
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().
next reply other threads:[~2019-07-19 17:03 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 17:03 Sean Christopherson [this message]
2019-07-19 17:40 ` [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace on i386 Andy Lutomirski
2019-07-22 17:16 ` Kees Cook
2019-07-22 18:31 ` Thomas Gleixner
2019-07-22 18:39 ` Kees Cook
2019-07-22 19:17 ` Andy Lutomirski
2019-07-22 23:28 ` Kees Cook
2019-07-22 23:47 ` Andy Lutomirski
2019-07-23 9:18 ` Peter Zijlstra
2019-07-23 14:04 ` Andy Lutomirski
2019-07-23 15:14 ` Peter Zijlstra
2019-07-23 21:55 ` Kees Cook
2019-07-23 22:55 ` Andy Lutomirski
2019-07-23 22:59 ` Thomas Gleixner
2019-07-23 23:43 ` Kees Cook
2019-07-23 23:56 ` Thomas Gleixner
2019-07-26 18:01 ` Sean Christopherson
2019-07-27 17:49 ` Andy Lutomirski
2019-07-27 18:43 ` Thomas Gleixner
2019-07-27 21:52 ` Thomas Gleixner
2019-07-28 0:33 ` Andy Lutomirski
2019-07-28 9:57 ` Arnd Bergmann
2019-07-28 10:30 ` Thomas Gleixner
2019-07-28 15:27 ` Arnd Bergmann
2019-07-28 18:14 ` Thomas Gleixner
2019-07-28 18:16 ` Thomas Gleixner
2019-07-28 11:13 ` Thomas Gleixner
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