From: Thomas Garnier <thgarnie@google.com>
To: "Martin Schwidefsky" <schwidefsky@de.ibm.com>,
"Heiko Carstens" <heiko.carstens@de.ibm.com>,
"Dave Hansen" <dave.hansen@intel.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Thomas Garnier" <thgarnie@google.com>,
"David Howells" <dhowells@redhat.com>,
"René Nyffenegger" <mail@renenyffenegger.ch>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
"Ingo Molnar" <mingo@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Pavel Tikhomirov" <ptikhomirov@virtuozzo.com>,
"Ingo Molnar" <mingo@redhat.com>,
"H . Peter Anvin" <hpa@zytor.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Rik van Riel" <riel@redhat.com>,
"Kees Cook" <keescook@chromium.org>,
"Josh Poimboeuf" <jpoimboe@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Brian Gerst" <brgerst@gmail.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
"Christian Borntraeger" <borntraeger@de.ibm.com>,
"Russell King" <linux@armlinux.org.uk>,
"Will Deacon" <will.deacon@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"James Morse" <james.morse@arm.com>
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, x86@kernel.org,
linux-arm-kernel@lists.infradead.org,
kernel-hardening@lists.openwall.com
Subject: [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode
Date: Thu, 27 Apr 2017 07:42:27 -0700 [thread overview]
Message-ID: <20170427144227.113630-1-thgarnie@google.com> (raw)
In-Reply-To: <CAJcbSZENjCgn3TNDGzCBBSOXMvbTX8mBO7Trugdb5VRzhxwmHg@mail.gmail.com>
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@google.com>
Tested-by: Kees Cook <keescook@chromium.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 ADDR_LIMIT_CHECK_PRE() \
+ bool user_caller = segment_eq(get_fs(), USER_DS)
+#define ADDR_LIMIT_CHECK_POST() \
+ if (user_caller) addr_limit_check_syscall()
+#else
+#define ADDR_LIMIT_CHECK_PRE()
+#define ADDR_LIMIT_CHECK_POST()
+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; \
+ ADDR_LIMIT_CHECK_PRE(); \
+ ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
+ ADDR_LIMIT_CHECK_POST(); \
__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 prev parent reply other threads:[~2017-04-27 14:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-26 18:34 [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode Thomas Garnier
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
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
2017-04-27 14:42 ` Thomas Garnier [this message]
2017-04-28 6:35 ` Ingo Molnar
2017-04-28 6:33 ` Ingo Molnar
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