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From: Kees Cook <keescook@chromium.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
	Thomas Garnier <thgarnie@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Will Drewry <wad@chromium.org>, Al Viro <viro@zeniv.linux.org.uk>,
	Dave Martin <Dave.Martin@arm.com>,
	Pratyush Anand <panand@redhat.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Arnd Bergmann <arnd@arndb.de>,
	David Howells <dhowells@redhat.com>, Yonghong Song <yhs@fb.com>,
	linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 1/4] syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check
Date: Thu,  7 Sep 2017 08:30:44 -0700	[thread overview]
Message-ID: <1504798247-48833-2-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1504798247-48833-1-git-send-email-keescook@chromium.org>

From: Thomas Garnier <thgarnie@google.com>

Use CHECK_DATA_CORRUPTION instead of BUG_ON to provide more flexibility
on address limit failures. By default, send a SIGKILL signal to kill the
current process preventing exploitation of a bad address limit.

Make the TIF_FSCHECK flag optional so ARM can use this function.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/syscalls.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 88951b795ee3..65e273aadada 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -219,21 +219,25 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
 	}								\
 	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
-#ifdef TIF_FSCHECK
 /*
  * 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_user_check(void)
 {
-
+#ifdef TIF_FSCHECK
 	if (!test_thread_flag(TIF_FSCHECK))
 		return;
+#endif
 
-	BUG_ON(!segment_eq(get_fs(), USER_DS));
+	if (CHECK_DATA_CORRUPTION(!segment_eq(get_fs(), USER_DS),
+				  "Invalid address limit on user-mode return"))
+		force_sig(SIGKILL, current);
+
+#ifdef TIF_FSCHECK
 	clear_thread_flag(TIF_FSCHECK);
-}
 #endif
+}
 
 asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special,
 			       qid_t id, void __user *addr);
-- 
2.7.4

WARNING: multiple messages have this Message-ID
From: keescook@chromium.org (Kees Cook)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/4] syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check
Date: Thu,  7 Sep 2017 08:30:44 -0700	[thread overview]
Message-ID: <1504798247-48833-2-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1504798247-48833-1-git-send-email-keescook@chromium.org>

From: Thomas Garnier <thgarnie@google.com>

Use CHECK_DATA_CORRUPTION instead of BUG_ON to provide more flexibility
on address limit failures. By default, send a SIGKILL signal to kill the
current process preventing exploitation of a bad address limit.

Make the TIF_FSCHECK flag optional so ARM can use this function.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/syscalls.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 88951b795ee3..65e273aadada 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -219,21 +219,25 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
 	}								\
 	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
-#ifdef TIF_FSCHECK
 /*
  * 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_user_check(void)
 {
-
+#ifdef TIF_FSCHECK
 	if (!test_thread_flag(TIF_FSCHECK))
 		return;
+#endif
 
-	BUG_ON(!segment_eq(get_fs(), USER_DS));
+	if (CHECK_DATA_CORRUPTION(!segment_eq(get_fs(), USER_DS),
+				  "Invalid address limit on user-mode return"))
+		force_sig(SIGKILL, current);
+
+#ifdef TIF_FSCHECK
 	clear_thread_flag(TIF_FSCHECK);
-}
 #endif
+}
 
 asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special,
 			       qid_t id, void __user *addr);
-- 
2.7.4

  reply	other threads:[~2017-09-07 15:31 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-07 15:30 [PATCH 0/4] Fix check address limit on user-mode Kees Cook
2017-09-07 15:30 ` Kees Cook
2017-09-07 15:30 ` Kees Cook [this message]
2017-09-07 15:30   ` [PATCH 1/4] syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check Kees Cook
2017-09-17 17:53   ` [tip:core/urgent] " tip-bot for Thomas Garnier
2017-09-07 15:30 ` [PATCH 2/4] Revert "arm/syscalls: Check address limit on user-mode return" Kees Cook
2017-09-07 15:30   ` Kees Cook
2017-09-17 17:54   ` [tip:core/urgent] " tip-bot for Thomas Garnier
2017-09-07 15:30 ` [PATCH 3/4] arm/syscalls: Optimize address limit check Kees Cook
2017-09-07 15:30   ` Kees Cook
2017-09-17 17:54   ` [tip:core/urgent] " tip-bot for Thomas Garnier
2017-09-07 15:30 ` [PATCH 4/4] arm64/syscalls: Move address limit check in loop Kees Cook
2017-09-07 15:30   ` Kees Cook
2017-09-12 18:27   ` Will Deacon
2017-09-12 18:27     ` Will Deacon
2017-09-12 18:28     ` Kees Cook
2017-09-12 18:28       ` Kees Cook
2017-09-12 18:28       ` Kees Cook
2017-09-13  8:00       ` Ingo Molnar
2017-09-13  8:00         ` Ingo Molnar
2017-09-13  8:00         ` Ingo Molnar
2017-09-17 17:54   ` [tip:core/urgent] " tip-bot for Thomas Garnier

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