linux-kernel - [PATCH 3.2 69/74] perf/x86: Check if user fp is valid

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Message-ID: <lsq.1507552234.339477223@decadent.org.uk>
Date:   Mon, 09 Oct 2017 13:30:34 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Arun Sharma" <asharma@...com>,
        "Ingo Molnar" <mingo@...nel.org>, "Jann Horn" <jannh@...gle.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: [PATCH 3.2 69/74] perf/x86: Check if user fp is valid

3.2.94-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arun Sharma <asharma@...com>

commit bc6ca7b342d5ae15c3ba3081fd40271b8039fb25 upstream.

Signed-off-by: Arun Sharma <asharma@...com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1334961696-19580-4-git-send-email-asharma@fb.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[bwh: Backported to 3.2: also add user_addr_max() macro]
Cc: Jann Horn <jannh@...gle.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -32,9 +32,9 @@
 
 #define segment_eq(a, b)	((a).seg == (b).seg)
 
-#define __addr_ok(addr)					\
-	((unsigned long __force)(addr) <		\
-	 (current_thread_info()->addr_limit.seg))
+#define user_addr_max() (current_thread_info()->addr_limit.seg)
+#define __addr_ok(addr) 	\
+	((unsigned long __force)(addr) < user_addr_max())
 
 /*
  * Test whether a block of memory is a valid user space address.
@@ -46,14 +46,14 @@
  * This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry...
  */
 
-#define __range_not_ok(addr, size)					\
+#define __range_not_ok(addr, size, limit)				\
 ({									\
 	unsigned long flag, roksum;					\
 	__chk_user_ptr(addr);						\
 	asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0"		\
 	    : "=&r" (flag), "=r" (roksum)				\
 	    : "1" (addr), "g" ((long)(size)),				\
-	      "rm" (current_thread_info()->addr_limit.seg));		\
+	      "rm" (limit));						\
 	flag;								\
 })
 
@@ -76,7 +76,8 @@
  * checks that the pointer is in the user space range - after calling
  * this function, memory access functions may still return -EFAULT.
  */
-#define access_ok(type, addr, size) (likely(__range_not_ok(addr, size) == 0))
+#define access_ok(type, addr, size) \
+	(likely(__range_not_ok(addr, size, user_addr_max()) == 0))
 
 /*
  * The exception table consists of pairs of addresses: the first is the
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1461,6 +1461,12 @@ perf_callchain_kernel(struct perf_callch
 	dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
 }
 
+static inline int
+valid_user_frame(const void __user *fp, unsigned long size)
+{
+	return (__range_not_ok(fp, size, TASK_SIZE) == 0);
+}
+
 #ifdef CONFIG_COMPAT
 static inline int
 perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
@@ -1485,6 +1491,9 @@ perf_callchain_user32(struct pt_regs *re
 		if (fp < compat_ptr(regs->sp))
 			break;
 
+		if (!valid_user_frame(fp, sizeof(frame)))
+			break;
+
 		perf_callchain_store(entry, frame.return_address);
 		fp = compat_ptr(frame.next_frame);
 	}
@@ -1531,6 +1540,9 @@ perf_callchain_user(struct perf_callchai
 		if ((unsigned long)fp < regs->sp)
 			break;
 
+		if (!valid_user_frame(fp, sizeof(frame)))
+			break;
+
 		perf_callchain_store(entry, frame.return_address);
 		fp = frame.next_frame;
 	}