[tip:core/urgent] syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check

From: tip-bot for Thomas Garnier
Date: Sun Sep 17 2017 - 13:59:50 EST

Commit-ID: bf29ed1567b67854dc13504f685c45a2ea9b2081
Gitweb: http://git.kernel.org/tip/bf29ed1567b67854dc13504f685c45a2ea9b2081
Author: Thomas Garnier <thgarnie@xxxxxxxxxx>
AuthorDate: Thu, 7 Sep 2017 08:30:44 -0700
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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 <thgarnie@xxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Pratyush Anand <panand@xxxxxxxxxx>
Cc: Dave Martin <Dave.Martin@xxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-api@xxxxxxxxxxxxxxx
Cc: Yonghong Song <yhs@xxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1504798247-48833-2-git-send-email-keescook@xxxxxxxxxxxx

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);