On Wed, Sep 30, 2020 at 10:19:16AM -0500, YiFei Zhu wrote: > From: YiFei Zhu <[email protected]> > > Currently the kernel does not provide an infrastructure to translate > architecture numbers to a human-readable name. Translating syscall > numbers to syscall names is possible through FTRACE_SYSCALL > infrastructure but it does not provide support for compat syscalls. > > This will create a file for each PID as /proc/pid/seccomp_cache. > The file will be empty when no seccomp filters are loaded, or be > in the format of: > <arch name> <decimal syscall number> <ALLOW | FILTER> > where ALLOW means the cache is guaranteed to allow the syscall, > and filter means the cache will pass the syscall to the BPF filter. > > For the docker default profile on x86_64 it looks like: > x86_64 0 ALLOW > x86_64 1 ALLOW > x86_64 2 ALLOW > x86_64 3 ALLOW > [...] > x86_64 132 ALLOW > x86_64 133 ALLOW > x86_64 134 FILTER > x86_64 135 FILTER > x86_64 136 FILTER > x86_64 137 ALLOW > x86_64 138 ALLOW > x86_64 139 FILTER > x86_64 140 ALLOW > x86_64 141 ALLOW > [...] > > This file is guarded by CONFIG_DEBUG_SECCOMP_CACHE with a default > of N because I think certain users of seccomp might not want the > application to know which syscalls are definitely usable. For > the same reason, it is also guarded by CAP_SYS_ADMIN. > > Suggested-by: Jann Horn <[email protected]> > Link: > https://lore.kernel.org/lkml/CAG48ez3Ofqp4crXGksLmZY6=fgrf_twyucg7pbkaetvbbop...@mail.gmail.com/ > Signed-off-by: YiFei Zhu <[email protected]> > --- > arch/Kconfig | 15 +++++++++++ > arch/x86/include/asm/seccomp.h | 3 +++ > fs/proc/base.c | 3 +++ > include/linux/seccomp.h | 5 ++++ > kernel/seccomp.c | 46 ++++++++++++++++++++++++++++++++++ > 5 files changed, 72 insertions(+) > > diff --git a/arch/Kconfig b/arch/Kconfig > index ca867b2a5d71..b840cadcc882 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -478,6 +478,7 @@ config HAVE_ARCH_SECCOMP_CACHE_NR_ONLY > - all the requirements for HAVE_ARCH_SECCOMP_FILTER > - SECCOMP_ARCH_DEFAULT > - SECCOMP_ARCH_DEFAULT_NR > + - SECCOMP_ARCH_DEFAULT_NAME > > config SECCOMP > prompt "Enable seccomp to safely execute untrusted bytecode" > @@ -532,6 +533,20 @@ config SECCOMP_CACHE_NR_ONLY > > endchoice > > +config DEBUG_SECCOMP_CACHE
naming nit: I prefer where what how order, so SECCOMP_CACHE_DEBUG. > + bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" > + depends on SECCOMP_CACHE_NR_ONLY > + depends on PROC_FS > + help > + This is enables /proc/pid/seccomp_cache interface to monitor > + seccomp cache data. The file format is subject to change. Reading > + the file requires CAP_SYS_ADMIN. > + > + This option is for debugging only. Enabling present the risk that > + an adversary may be able to infer the seccomp filter logic. > + > + If unsure, say N. > + > config HAVE_ARCH_STACKLEAK > bool > help > diff --git a/arch/x86/include/asm/seccomp.h b/arch/x86/include/asm/seccomp.h > index 7b3a58271656..33ccc074be7a 100644 > --- a/arch/x86/include/asm/seccomp.h > +++ b/arch/x86/include/asm/seccomp.h > @@ -19,13 +19,16 @@ > #ifdef CONFIG_X86_64 > # define SECCOMP_ARCH_DEFAULT AUDIT_ARCH_X86_64 > # define SECCOMP_ARCH_DEFAULT_NR NR_syscalls > +# define SECCOMP_ARCH_DEFAULT_NAME "x86_64" > # ifdef CONFIG_COMPAT > # define SECCOMP_ARCH_COMPAT AUDIT_ARCH_I386 > # define SECCOMP_ARCH_COMPAT_NR IA32_NR_syscalls > +# define SECCOMP_ARCH_COMPAT_NAME "x86_32" I think this should be "ia32"? Is there a good definitive guide on this naming convention? -- Kees Cook
