[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 9 Mar 2017 13:32:46 +0100
From: Christian Borntraeger <borntraeger@...ibm.com>
To: Thomas Garnier <thgarnie@...gle.com>, David Howells
<dhowells@...hat.com>,
Dave Hansen <dave.hansen@...el.com>, Arnd Bergmann <arnd@...db.de>,
Al Viro <viro@...iv.linux.org.uk>,
René Nyffenegger <mail@...enyffenegger.ch>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook
<keescook@...omium.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
"David S . Miller" <davem@...emloft.net>,
Andy Lutomirski <luto@...nel.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Nicolas Pitre <nicolas.pitre@...aro.org>,
Petr Mladek <pmladek@...e.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Helge Deller <deller@....de>, Rik van Riel <riel@...hat.com>,
Ingo Molnar <mingo@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
John Stultz <john.stultz@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Stephen Smalley
<sds@...ho.nsa.gov>,
Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>,
Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>, Borislav Petkov <bp@...en8.de>,
Josh Poimboeuf <jpoimboe@...hat.com>, Brian Gerst <brgerst@...il.com>,
Jan Beulich <JBeulich@...e.com>,
"Luis R . Rodriguez" <mcgrof@...nel.org>,
He Chen <he.chen@...ux.intel.com>,
Russell King <linux@...linux.org.uk>,
Will Deacon <will.deacon@....com>,
Catalin Marinas
<catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>, James Morse <james.morse@....com>,
Pratyush Anand <panand@...hat.com>,
Vladimir Murzin <vladimir.murzin@....com>,
Chris Metcalf <cmetcalf@...lanox.com>,
Andre Przywara <andre.przywara@....com>
Cc: linux-api@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
linux-arm-kernel@...ts.infradead.org,
kernel-hardening@...ts.openwall.com,
Heiko Carstens <heiko.carstens@...ibm.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
linux-s390 <linux-s390@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] syscalls: Restore address limit after a syscall
On 03/09/2017 02:24 AM, Thomas Garnier wrote:
> This patch ensures a syscall does not return to user-mode with a kernel
> address limit. If that happened, a process can corrupt kernel-mode
> memory and elevate privileges.
>
> For example, it would mitigation this bug:
>
> - https://bugs.chromium.org/p/project-zero/issues/detail?id=990
>
> If the CONFIG_BUG_ON_DATA_CORRUPTION option is enabled, an incorrect
> state will result in a BUG_ON.
>
> The CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE option is also
> added so each architecture can optimize this change.
>
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
> Based on next-20170308
> ---
> include/linux/syscalls.h | 19 +++++++++++++++++++
> init/Kconfig | 7 +++++++
> kernel/sys.c | 8 ++++++++
> 3 files changed, 34 insertions(+)
>
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 980c3c9b06f8..78a2268ecd6e 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -191,6 +191,22 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> SYSCALL_METADATA(sname, x, __VA_ARGS__) \
> __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
>
> +asmlinkage void verify_pre_usermode_state(void);
> +
> +#ifndef CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> +static inline bool has_user_ds(void) {
> + bool ret = segment_eq(get_fs(), USER_DS);
> + // Prevent re-ordering the call
> + barrier();
> + return ret;
> +}
Can you please disable that for s390? (e.g. by setting
CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE for s390)
We have a separate address space for kernel/user so the logic will
be slightly different and is already handled in
commit b5a882fcf146c87cb6b67c6df353e1c042b8773d
Author: Heiko Carstens <heiko.carstens@...ibm.com>
Date: Fri Feb 17 08:13:28 2017 +0100
s390: restore address space when returning to user space
> +#else
> +static inline bool has_user_ds(void) {
> + return false;
> +}
> +#endif
> +
> +
> #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
> #define __SYSCALL_DEFINEx(x, name, ...) \
> asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
> @@ -199,7 +215,10 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
> asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
> { \
> + bool user_caller = has_user_ds(); \
> long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
> + if (user_caller) \
> + verify_pre_usermode_state(); \
> __MAP(x,__SC_TEST,__VA_ARGS__); \
> __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
> return ret; \
> diff --git a/init/Kconfig b/init/Kconfig
> index c859c993c26f..c4efc3a95e4a 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1929,6 +1929,13 @@ config PROFILING
> config TRACEPOINTS
> bool
>
> +#
> +# Set by each architecture that want to optimize how verify_pre_usermode_state
> +# is called.
> +#
> +config ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> + bool
> +
> source "arch/Kconfig"
>
> endmenu # General setup
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 196c7134bee6..411163ac9dc3 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2459,3 +2459,11 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
> return 0;
> }
> #endif /* CONFIG_COMPAT */
> +
> +/* Called before coming back to user-mode */
> +asmlinkage void verify_pre_usermode_state(void)
> +{
> + if (CHECK_DATA_CORRUPTION(!segment_eq(get_fs(), USER_DS),
> + "incorrect get_fs() on user-mode return"))
> + set_fs(USER_DS);
> +}
>
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
