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Date:   Sun, 17 Sep 2017 10:53:35 -0700
From:   tip-bot for Thomas Garnier <>
Subject: [tip:core/urgent] syscalls: Use CHECK_DATA_CORRUPTION for

Commit-ID:  bf29ed1567b67854dc13504f685c45a2ea9b2081
Author:     Thomas Garnier <>
AuthorDate: Thu, 7 Sep 2017 08:30:44 -0700
Committer:  Thomas Gleixner <>
CommitDate: Sun, 17 Sep 2017 19:45:32 +0200

syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check

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 <>
Signed-off-by: Kees Cook <>
Signed-off-by: Thomas Gleixner <>
Cc: Pratyush Anand <>
Cc: Dave Martin <>
Cc: Will Drewry <>
Cc: Arnd Bergmann <>
Cc: Catalin Marinas <>
Cc: Will Deacon <>
Cc: Russell King <>
Cc: Andy Lutomirski <>
Cc: David Howells <>
Cc: Dave Hansen <>
Cc: Al Viro <>
Cc: Yonghong Song <>

 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 95606a2..a78186d 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -221,21 +221,25 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
 	}								\
 	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
  * 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)
 	if (!test_thread_flag(TIF_FSCHECK))
-	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);
 asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special,
 			       qid_t id, void __user *addr);

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