From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Wed, 13 Dec 2017 15:50:21 +0000 (+0000)
Subject: aarch64: enforce >=64K guard size [BZ #26691]
X-Git-Tag: glibc-2.33~448
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=238032ead6f34c41542890b968d973eb5c839673;p=thirdparty%2Fglibc.git

aarch64: enforce >=64K guard size [BZ #26691]

There are several compiler implementations that allow large stack
allocations to jump over the guard page at the end of the stack and
corrupt memory beyond that. See CVE-2017-1000364.

Compilers can emit code to probe the stack such that the guard page
cannot be skipped, but on aarch64 the probe interval is 64K by default
instead of the minimum supported page size (4K).

This patch enforces at least 64K guard on aarch64 unless the guard
is disabled by setting its size to 0.  For backward compatibility
reasons the increased guard is not reported, so it is only observable
by exhausting the address space or parsing /proc/self/maps on linux.

On other targets the patch has no effect. If the stack probe interval
is larger than a page size on a target then ARCH_MIN_GUARD_SIZE can
be defined to get large enough stack guard on libc allocated stacks.

The patch does not affect threads with user allocated stacks.

Fixes bug 26691.
---

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 4ae4b5a9862..4b45f8c884b 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -521,6 +521,7 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
     {
       /* Allocate some anonymous memory.  If possible use the cache.  */
       size_t guardsize;
+      size_t reported_guardsize;
       size_t reqsize;
       void *mem;
       const int prot = (PROT_READ | PROT_WRITE
@@ -531,8 +532,17 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
       assert (size != 0);
 
       /* Make sure the size of the stack is enough for the guard and
-	 eventually the thread descriptor.  */
+	 eventually the thread descriptor.  On some targets there is
+	 a minimum guard size requirement, ARCH_MIN_GUARD_SIZE, so
+	 internally enforce it (unless the guard was disabled), but
+	 report the original guard size for backward compatibility:
+	 before POSIX 2008 the guardsize was specified to be one page
+	 by default which is observable via pthread_attr_getguardsize
+	 and pthread_getattr_np.  */
       guardsize = (attr->guardsize + pagesize_m1) & ~pagesize_m1;
+      reported_guardsize = guardsize;
+      if (guardsize > 0 && guardsize < ARCH_MIN_GUARD_SIZE)
+	guardsize = ARCH_MIN_GUARD_SIZE;
       if (guardsize < attr->guardsize || size + guardsize < guardsize)
 	/* Arithmetic overflow.  */
 	return EINVAL;
@@ -740,7 +750,7 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
       /* The pthread_getattr_np() calls need to get passed the size
 	 requested in the attribute, regardless of how large the
 	 actually used guardsize is.  */
-      pd->reported_guardsize = guardsize;
+      pd->reported_guardsize = reported_guardsize;
     }
 
   /* Initialize the lock.  We have to do this unconditionally since the
diff --git a/sysdeps/aarch64/nptl/pthreaddef.h b/sysdeps/aarch64/nptl/pthreaddef.h
index 892b869fc23..b865fd5fab5 100644
--- a/sysdeps/aarch64/nptl/pthreaddef.h
+++ b/sysdeps/aarch64/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE (64 * 1024)
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN 16
 
diff --git a/sysdeps/alpha/nptl/pthreaddef.h b/sysdeps/alpha/nptl/pthreaddef.h
index 6ec8f49f39d..c710b04845d 100644
--- a/sysdeps/alpha/nptl/pthreaddef.h
+++ b/sysdeps/alpha/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(4 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  The ABI requires 16.  */
 #define STACK_ALIGN		16
 
diff --git a/sysdeps/arc/nptl/pthreaddef.h b/sysdeps/arc/nptl/pthreaddef.h
index 5c2b752beca..844b2137291 100644
--- a/sysdeps/arc/nptl/pthreaddef.h
+++ b/sysdeps/arc/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		4
 
diff --git a/sysdeps/arm/nptl/pthreaddef.h b/sysdeps/arm/nptl/pthreaddef.h
index 5b05f2a8bd2..3e21cbd39a6 100644
--- a/sysdeps/arm/nptl/pthreaddef.h
+++ b/sysdeps/arm/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  SSE requires 16
    bytes.  */
 #define STACK_ALIGN		16
diff --git a/sysdeps/csky/nptl/pthreaddef.h b/sysdeps/csky/nptl/pthreaddef.h
index 98b9546b12c..f4b0b4c8473 100644
--- a/sysdeps/csky/nptl/pthreaddef.h
+++ b/sysdeps/csky/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		8
 
diff --git a/sysdeps/hppa/nptl/pthreaddef.h b/sysdeps/hppa/nptl/pthreaddef.h
index 9fab974e7d1..5dd4fec20db 100644
--- a/sysdeps/hppa/nptl/pthreaddef.h
+++ b/sysdeps/hppa/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(8 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		64
 
diff --git a/sysdeps/i386/nptl/pthreaddef.h b/sysdeps/i386/nptl/pthreaddef.h
index 65d5bc9b2ef..db833351c6f 100644
--- a/sysdeps/i386/nptl/pthreaddef.h
+++ b/sysdeps/i386/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  SSE requires 16
    bytes.  */
 #define STACK_ALIGN		16
diff --git a/sysdeps/ia64/nptl/pthreaddef.h b/sysdeps/ia64/nptl/pthreaddef.h
index 42a95e6b24b..26c509abe25 100644
--- a/sysdeps/ia64/nptl/pthreaddef.h
+++ b/sysdeps/ia64/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(32 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* IA-64 uses a normal stack and a register stack.  */
 #define NEED_SEPARATE_REGISTER_STACK
 
diff --git a/sysdeps/m68k/nptl/pthreaddef.h b/sysdeps/m68k/nptl/pthreaddef.h
index baca43951dc..8d0253ba4cf 100644
--- a/sysdeps/m68k/nptl/pthreaddef.h
+++ b/sysdeps/m68k/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		16
 
diff --git a/sysdeps/microblaze/nptl/pthreaddef.h b/sysdeps/microblaze/nptl/pthreaddef.h
index c043372f446..73b4a42971f 100644
--- a/sysdeps/microblaze/nptl/pthreaddef.h
+++ b/sysdeps/microblaze/nptl/pthreaddef.h
@@ -22,6 +22,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE  (2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN         16
 
diff --git a/sysdeps/mips/nptl/pthreaddef.h b/sysdeps/mips/nptl/pthreaddef.h
index fa232b0c783..8305c23940c 100644
--- a/sysdeps/mips/nptl/pthreaddef.h
+++ b/sysdeps/mips/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		16
 
diff --git a/sysdeps/nios2/nptl/pthreaddef.h b/sysdeps/nios2/nptl/pthreaddef.h
index 4ae7d4581c9..590e3f87747 100644
--- a/sysdeps/nios2/nptl/pthreaddef.h
+++ b/sysdeps/nios2/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		4
 
diff --git a/sysdeps/powerpc/nptl/pthreaddef.h b/sysdeps/powerpc/nptl/pthreaddef.h
index 4abdc480c4b..70e55b70f01 100644
--- a/sysdeps/powerpc/nptl/pthreaddef.h
+++ b/sysdeps/powerpc/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(4 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  The ABI requires 16
    bytes (for both 32-bit and 64-bit PowerPC).  */
 #define STACK_ALIGN		16
diff --git a/sysdeps/riscv/nptl/pthreaddef.h b/sysdeps/riscv/nptl/pthreaddef.h
index 146c04f63a6..b45359faf7e 100644
--- a/sysdeps/riscv/nptl/pthreaddef.h
+++ b/sysdeps/riscv/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		16
 
diff --git a/sysdeps/s390/nptl/pthreaddef.h b/sysdeps/s390/nptl/pthreaddef.h
index e087e1cddfb..c218271fc39 100644
--- a/sysdeps/s390/nptl/pthreaddef.h
+++ b/sysdeps/s390/nptl/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  SSE requires 16
    bytes.  */
 #define STACK_ALIGN		16
diff --git a/sysdeps/sh/nptl/pthreaddef.h b/sysdeps/sh/nptl/pthreaddef.h
index 12106e79e1b..50cedcefa6c 100644
--- a/sysdeps/sh/nptl/pthreaddef.h
+++ b/sysdeps/sh/nptl/pthreaddef.h
@@ -20,6 +20,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		8
 
diff --git a/sysdeps/sparc/sparc32/pthreaddef.h b/sysdeps/sparc/sparc32/pthreaddef.h
index 403fa3e3400..41de22b3be8 100644
--- a/sysdeps/sparc/sparc32/pthreaddef.h
+++ b/sysdeps/sparc/sparc32/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		16
 
diff --git a/sysdeps/sparc/sparc64/pthreaddef.h b/sysdeps/sparc/sparc64/pthreaddef.h
index 0a0841262ad..363b0f9e413 100644
--- a/sysdeps/sparc/sparc64/pthreaddef.h
+++ b/sysdeps/sparc/sparc64/pthreaddef.h
@@ -18,6 +18,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(4 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  */
 #define STACK_ALIGN		16
 
diff --git a/sysdeps/x86_64/nptl/pthreaddef.h b/sysdeps/x86_64/nptl/pthreaddef.h
index d49848da3c1..5554876bfcd 100644
--- a/sysdeps/x86_64/nptl/pthreaddef.h
+++ b/sysdeps/x86_64/nptl/pthreaddef.h
@@ -19,6 +19,9 @@
 /* Default stack size.  */
 #define ARCH_STACK_DEFAULT_SIZE	(2 * 1024 * 1024)
 
+/* Minimum guard size.  */
+#define ARCH_MIN_GUARD_SIZE 0
+
 /* Required stack pointer alignment at beginning.  SSE requires 16
    bytes.  */
 #define STACK_ALIGN		16