From: Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
To: "Martin Schwidefsky"
<schwidefsky-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
"Heiko Carstens"
<heiko.carstens-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
"Dave Hansen"
<dave.hansen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
"Arnd Bergmann" <arnd-r2nGTMty4D4@public.gmane.org>,
"David Howells"
<dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"René Nyffenegger"
<mail-gLCNRsNSrVdVZEhyV+6z5nIPMjoJpjVV@public.gmane.org>,
"Thomas Garnier"
<thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
"Andrew Morton"
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
"Paul E . McKenney"
<paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
"Ingo Molnar" <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
"Eric W . Biederman"
<ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>,
"Thomas Gleixner" <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
"Oleg Nesterov" <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Pavel Tikhomirov"
<ptikhomirov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>,
"Ingo Molnar" <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"H . Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
"Andy Lutomirski" <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
"Paolo Bonzini"
<pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Kees Cook" <keescook@chromium.o>
Cc: linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
kernel-hardening-ZwoEplunGu1jrUoiu81ncdBPR1lH4CV8@public.gmane.org
Subject: [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode
Date: Wed, 26 Apr 2017 11:34:22 -0700 [thread overview]
Message-ID: <20170426183425.32158-1-thgarnie@google.com> (raw)
Ensure that a syscall does not return to user-mode with a kernel address
limit. If that happens, a process can corrupt kernel-mode memory and
elevate privileges [1].
The CONFIG_ADDR_LIMIT_CHECK option disables the generic check so each
architecture can create optimized versions.
[1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990
Signed-off-by: Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Tested-by: Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
Based on next-20170426
---
arch/s390/Kconfig | 1 +
include/linux/syscalls.h | 27 ++++++++++++++++++++++++++-
init/Kconfig | 6 ++++++
kernel/sys.c | 13 +++++++++++++
4 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index d25435d94b6e..164de1d24e92 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -103,6 +103,7 @@ config S390
select ARCH_INLINE_WRITE_UNLOCK_BH
select ARCH_INLINE_WRITE_UNLOCK_IRQ
select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
+ select ADDR_LIMIT_CHECK
select ARCH_SAVE_PAGE_KEYS if HIBERNATION
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 980c3c9b06f8..ebde64f1622c 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -191,6 +191,28 @@ extern struct trace_event_functions exit_syscall_print_funcs;
SYSCALL_METADATA(sname, x, __VA_ARGS__) \
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
+
+/*
+ * Called before coming back to user-mode. Returning to user-mode with an
+ * address limit different than USER_DS can allow to overwrite kernel memory.
+ */
+static inline void addr_limit_check_syscall(void)
+{
+ BUG_ON(!segment_eq(get_fs(), USER_DS));
+}
+
+#ifndef CONFIG_ADDR_LIMIT_CHECK
+#define __CHECK_USERMODE_SYSCALL() \
+ bool user_caller = segment_eq(get_fs(), USER_DS)
+#define __VERIFY_ADDR_LIMIT() \
+ if (user_caller) addr_limit_check_syscall()
+#else
+#define __CHECK_USERMODE_SYSCALL()
+#define __VERIFY_ADDR_LIMIT()
+asmlinkage void addr_limit_check_failed(void) __noreturn;
+#endif
+
+
#define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
#define __SYSCALL_DEFINEx(x, name, ...) \
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
@@ -199,7 +221,10 @@ 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__)) \
{ \
- long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
+ long ret; \
+ __CHECK_USERMODE_SYSCALL(); \
+ ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
+ __VERIFY_ADDR_LIMIT(); \
__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 42a346b0df43..599d9fe30703 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1961,6 +1961,12 @@ config PROFILING
config TRACEPOINTS
bool
+config ADDR_LIMIT_CHECK
+ bool
+ help
+ Disable the generic address limit check. Allow each architecture to
+ optimize how and when the verification is done.
+
source "arch/Kconfig"
endmenu # General setup
diff --git a/kernel/sys.c b/kernel/sys.c
index 8a94b4eabcaa..a1cbcd715d62 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2458,3 +2458,16 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
return 0;
}
#endif /* CONFIG_COMPAT */
+
+#ifdef CONFIG_ADDR_LIMIT_CHECK
+/*
+ * Used when an architecture specific implementation detects an invalid address
+ * limit. This function does not return.
+ */
+asmlinkage void addr_limit_check_failed(void)
+{
+ /* Try to fail on the generic address limit check */
+ addr_limit_check_syscall();
+ panic("Invalid address limit before returning to user-mode");
+}
+#endif
--
2.13.0.rc0.306.g87b477812d-goog
next reply other threads:[~2017-04-26 18:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-26 18:34 Thomas Garnier [this message]
2017-04-26 18:34 ` [PATCH v8 2/4] x86/syscalls: Optimize address limit check Thomas Garnier
2017-04-26 18:34 ` [PATCH v8 3/4] arm/syscalls: " Thomas Garnier
2017-04-26 18:34 ` [PATCH v8 4/4] arm64/syscalls: " Thomas Garnier
[not found] ` <20170426183425.32158-1-thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2017-04-27 6:49 ` [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode Ingo Molnar
2017-04-27 14:16 ` Thomas Garnier
[not found] ` <CAJcbSZENjCgn3TNDGzCBBSOXMvbTX8mBO7Trugdb5VRzhxwmHg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-27 14:42 ` Thomas Garnier
[not found] ` <20170427144227.113630-1-thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2017-04-28 6:35 ` Ingo Molnar
2017-04-28 6:33 ` Ingo Molnar
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