selftests/x86/mpx: Fix incorrect bounds with old _sigfault

Web:        https://git.kernel.org/torvalds/c/961888b1d76d84efc66a8f5604b06ac12ac2f978
Commit:     961888b1d76d84efc66a8f5604b06ac12ac2f978
Parent:     1299ef1d8870d2d9f09a5aadf2f8b2c887c2d033
Refname:    refs/heads/master
Author:     Rui Wang <[email protected]>
AuthorDate: Mon Dec 18 16:34:10 2017 +0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Thu Feb 15 01:15:52 2018 +0100

    selftests/x86/mpx: Fix incorrect bounds with old _sigfault
    
    For distributions with old userspace header files, the _sigfault
    structure is different. mpx-mini-test fails with the following
    error:
    
      [root@Purley]# mpx-mini-test_64 tabletest
      XSAVE is supported by HW & OS
      XSAVE processor supported state mask: 0x2ff
      XSAVE OS supported state mask: 0x2ff
       BNDREGS: size: 64 user: 1 supervisor: 0 aligned: 0
        BNDCSR: size: 64 user: 1 supervisor: 0 aligned: 0
      starting mpx bounds table test
      ERROR: siginfo bounds do not match shadow bounds for register 0
    
    Fix it by using the correct offset of _lower/_upper in _sigfault.
    RHEL needs this patch to work.
    
    Signed-off-by: Rui Wang <[email protected]>
    Cc: Linus Torvalds <[email protected]>
    Cc: Peter Zijlstra <[email protected]>
    Cc: Thomas Gleixner <[email protected]>
    Cc: [email protected]
    Fixes: e754aedc26ef ("x86/mpx, selftests: Add MPX self test")
    Link: http://lkml.kernel.org/r/[email protected]
    Signed-off-by: Ingo Molnar <[email protected]>
---
 tools/testing/selftests/x86/mpx-mini-test.c | 32 +++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/x86/mpx-mini-test.c b/tools/testing/selftests/x86/mpx-mini-test.c
index ec0f6b45ce8b..9c0325e1ea68 100644
--- a/tools/testing/selftests/x86/mpx-mini-test.c
+++ b/tools/testing/selftests/x86/mpx-mini-test.c
@@ -315,11 +315,39 @@ static inline void *__si_bounds_upper(siginfo_t *si)
 	return si->si_upper;
 }
 #else
+
+/*
+ * This deals with old version of _sigfault in some distros:
+ *
+
+old _sigfault:
+        struct {
+            void *si_addr;
+	} _sigfault;
+
+new _sigfault:
+	struct {
+		void __user *_addr;
+		int _trapno;
+		short _addr_lsb;
+		union {
+			struct {
+				void __user *_lower;
+				void __user *_upper;
+			} _addr_bnd;
+			__u32 _pkey;
+		};
+	} _sigfault;
+ *
+ */
+
 static inline void **__si_bounds_hack(siginfo_t *si)
 {
 	void *sigfault = &si->_sifields._sigfault;
 	void *end_sigfault = sigfault + sizeof(si->_sifields._sigfault);
-	void **__si_lower = end_sigfault;
+	int *trapno = (int*)end_sigfault;
+	/* skip _trapno and _addr_lsb */
+	void **__si_lower = (void**)(trapno + 2);
 
 	return __si_lower;
 }
@@ -331,7 +359,7 @@ static inline void *__si_bounds_lower(siginfo_t *si)
 
 static inline void *__si_bounds_upper(siginfo_t *si)
 {
-	return (*__si_bounds_hack(si)) + sizeof(void *);
+	return *(__si_bounds_hack(si) + 1);
 }
 #endif
 
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