lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20220120160822.852009966@infradead.org>
Date:   Thu, 20 Jan 2022 16:55:21 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     mingo@...hat.com, tglx@...utronix.de, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-api@...r.kernel.org, x86@...nel.org, peterz@...radead.org,
        pjt@...gle.com, posk@...gle.com, avagin@...gle.com,
        jannh@...gle.com, tdelisle@...terloo.ca, mark.rutland@....com,
        posk@...k.io, Sean Christopherson <seanjc@...gle.com>
Subject: [RFC][PATCH v2 4/5] x86/uaccess: Implement unsafe_try_cmpxchg_user()

Do try_cmpxchg() loops on userspace addresses.

Cc: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/uaccess.h |   67 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -342,6 +342,24 @@ do {									\
 		     : [umem] "m" (__m(addr))				\
 		     : : label)
 
+#define __try_cmpxchg_user_asm(itype, ltype, _ptr, _pold, _new, label)	({ \
+	bool success;							\
+	__typeof__(_ptr) _old = (__typeof__(_ptr))(_pold);		\
+	__typeof__(*(_ptr)) __old = *_old;				\
+	__typeof__(*(_ptr)) __new = (_new);				\
+	asm_volatile_goto("\n"						\
+		     "1: " LOCK_PREFIX "cmpxchg"itype" %[new], %[ptr]\n"\
+		     _ASM_EXTABLE_UA(1b, %l[label])			\
+		     : CC_OUT(z) (success),				\
+		       [ptr] "+m" (*_ptr),				\
+		       [old] "+a" (__old)				\
+		     : [new] ltype (__new)				\
+		     : "memory", "cc"					\
+		     : label);						\
+	if (unlikely(!success))						\
+		*_old = __old;						\
+	likely(success);					})
+
 #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
 
 #ifdef CONFIG_X86_32
@@ -407,6 +425,30 @@ do {									\
 		     : [umem] "m" (__m(addr)),				\
 		       "0" (err))
 
+#define __try_cmpxchg_user_asm(itype, ltype, _ptr, _pold, _new, label)	({ \
+	int __err = 0;							\
+	bool success;							\
+	__typeof__(_ptr) _old = (__typeof__(_ptr))(_pold);		\
+	__typeof__(*(_ptr)) __old = *_old;				\
+	__typeof__(*(_ptr)) __new = (_new);				\
+	asm volatile("\n"						\
+		     "1: " LOCK_PREFIX "cmpxchg"itype" %[new], %[ptr]\n"\
+		     CC_SET(z)						\
+		     "2:\n"						\
+		     _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG,	\
+					   %[errout])			\
+		     : CC_OUT(z) (success),				\
+		       [errout] "+r" (__err),				\
+		       [ptr] "+m" (*_ptr),				\
+		       [old] "+a" (__old)				\
+		     : [new] ltype (__new)				\
+		     : "memory", "cc");					\
+	if (unlikely(__err))						\
+		goto label;						\
+	if (unlikely(!success))						\
+		*_old = __old;						\
+	likely(success);					})
+
 #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
 
 /* FIXME: this hack is definitely wrong -AK */
@@ -501,6 +543,31 @@ do {										\
 } while (0)
 #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
 
+extern void __try_cmpxchg_user_wrong_size(void);
+
+#define unsafe_try_cmpxchg_user(_ptr, _oldp, _nval, _label) ({		\
+	__typeof__(*(_ptr)) __ret;					\
+	switch (sizeof(__ret)) {					\
+	case 1:	__ret = __try_cmpxchg_user_asm("b", "q",		\
+					       (_ptr), (_oldp),		\
+					       (_nval), _label);	\
+		break;							\
+	case 2:	__ret = __try_cmpxchg_user_asm("w", "r",		\
+					       (_ptr), (_oldp),		\
+					       (_nval), _label);	\
+		break;							\
+	case 4:	__ret = __try_cmpxchg_user_asm("l", "r",		\
+					       (_ptr), (_oldp),		\
+					       (_nval), _label);	\
+		break;							\
+	case 8:	__ret = __try_cmpxchg_user_asm("q", "r",		\
+					       (_ptr), (_oldp),		\
+					       (_nval), _label);	\
+		break;							\
+	default: __try_cmpxchg_user_wrong_size();			\
+	}								\
+	__ret;						})
+
 /*
  * We want the unsafe accessors to always be inlined and use
  * the error labels - thus the macro games.


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ