BACKPORT: kprobes: Unpoison stack in jprobe_return() for KASAN

I observed false KSAN positives in the sctp code, when
sctp uses jprobe_return() in jsctp_sf_eat_sack().

The stray 0xf4 in shadow memory are stack redzones:

[     ] ==================================================================
[     ] BUG: KASAN: stack-out-of-bounds in memcmp+0xe9/0x150 at addr ffff88005e48f480
[     ] Read of size 1 by task syz-executor/18535
[     ] page:ffffea00017923c0 count:0 mapcount:0 mapping:          (null) index:0x0
[     ] flags: 0x1fffc0000000000()
[     ] page dumped because: kasan: bad access detected
[     ] CPU: 1 PID: 18535 Comm: syz-executor Not tainted 4.8.0+ #28
[     ] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[     ]  ffff88005e48f2d0 ffffffff82d2b849 ffffffff0bc91e90 fffffbfff10971e8
[     ]  ffffed000bc91e90 ffffed000bc91e90 0000000000000001 0000000000000000
[     ]  ffff88005e48f480 ffff88005e48f350 ffffffff817d3169 ffff88005e48f370
[     ] Call Trace:
[     ]  [<ffffffff82d2b849>] dump_stack+0x12e/0x185
[     ]  [<ffffffff817d3169>] kasan_report+0x489/0x4b0
[     ]  [<ffffffff817d31a9>] __asan_report_load1_noabort+0x19/0x20
[     ]  [<ffffffff82d49529>] memcmp+0xe9/0x150
[     ]  [<ffffffff82df7486>] depot_save_stack+0x176/0x5c0
[     ]  [<ffffffff817d2031>] save_stack+0xb1/0xd0
[     ]  [<ffffffff817d27f2>] kasan_slab_free+0x72/0xc0
[     ]  [<ffffffff817d05b8>] kfree+0xc8/0x2a0
[     ]  [<ffffffff85b03f19>] skb_free_head+0x79/0xb0
[     ]  [<ffffffff85b0900a>] skb_release_data+0x37a/0x420
[     ]  [<ffffffff85b090ff>] skb_release_all+0x4f/0x60
[     ]  [<ffffffff85b11348>] consume_skb+0x138/0x370
[     ]  [<ffffffff8676ad7b>] sctp_chunk_put+0xcb/0x180
[     ]  [<ffffffff8676ae88>] sctp_chunk_free+0x58/0x70
[     ]  [<ffffffff8677fa5f>] sctp_inq_pop+0x68f/0xef0
[     ]  [<ffffffff8675ee36>] sctp_assoc_bh_rcv+0xd6/0x4b0
[     ]  [<ffffffff8677f2c1>] sctp_inq_push+0x131/0x190
[     ]  [<ffffffff867bad69>] sctp_backlog_rcv+0xe9/0xa20
[ ... ]
[     ] Memory state around the buggy address:
[     ]  ffff88005e48f380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[     ]  ffff88005e48f400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[     ] >ffff88005e48f480: f4 f4 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[     ]                    ^
[     ]  ffff88005e48f500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[     ]  ffff88005e48f580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[     ] ==================================================================

KASAN stack instrumentation poisons stack redzones on function entry
and unpoisons them on function exit. If a function exits abnormally
(e.g. with a longjmp like jprobe_return()), stack redzones are left
poisoned. Later this leads to random KASAN false reports.

Unpoison stack redzones in the frames we are going to jump over
before doing actual longjmp in jprobe_return().

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: kasan-dev@googlegroups.com
Cc: surovegin@google.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1476454043-101898-1-git-send-email-dvyukov@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Bug: 64145065
(cherry-picked from 9f7d416c36124667c406978bcb39746589c35d7f)
Change-Id: I84e4fac44265a69f615601266b3415147dade633
Signed-off-by: Paul Lawrence <paullawrence@google.com>

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 99d293ea2b496a8646847715afe3d15bee98768e..3eb804335458b5ee904e0d6c279d505b3e7ecff0 100644 (file)
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -49,7 +49,7 @@
 #include <linux/kdebug.h>
 #include <linux/kallsyms.h>
 #include <linux/ftrace.h>
-
+#include <linux/kasan.h>
 #include <asm/cacheflush.h>
 #include <asm/desc.h>
 #include <asm/pgtable.h>
@@ -1078,6 +1078,9 @@ void jprobe_return(void)
 {
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 
+       /* Unpoison stack redzones in the frames we are going to jump over. */
+       kasan_unpoison_stack_above_sp_to(kcb->jprobe_saved_sp);
+
        asm volatile (
 #ifdef CONFIG_X86_64
                        "       xchg   %%rbx,%%rsp      \n"

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index d600303306eb7b54bbc68b62c89243e778f2a75c..820c0ad54a0117596e63bae6845b1ebd771c3412 100644 (file)
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -44,6 +44,7 @@ static inline void kasan_disable_current(void)
 void kasan_unpoison_shadow(const void *address, size_t size);
 
 void kasan_unpoison_task_stack(struct task_struct *task);
+void kasan_unpoison_stack_above_sp_to(const void *watermark);
 
 void kasan_alloc_pages(struct page *page, unsigned int order);
 void kasan_free_pages(struct page *page, unsigned int order);
@@ -85,6 +86,7 @@ size_t kasan_metadata_size(struct kmem_cache *cache);
 static inline void kasan_unpoison_shadow(const void *address, size_t size) {}
 
 static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
+static inline void kasan_unpoison_stack_above_sp_to(const void *watermark) {}
 
 static inline void kasan_enable_current(void) {}
 static inline void kasan_disable_current(void) {}

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 88af13c00d3cbfedb1d6d42ef5ddcf6ca9a50cab..70c009741aab705c6bb344df1f1851d9582bc7a7 100644 (file)
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -34,6 +34,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>
+#include <linux/bug.h>
 
 #include "kasan.h"
 #include "../slab.h"
@@ -62,7 +63,7 @@ void kasan_unpoison_shadow(const void *address, size_t size)
        }
 }
 
-static void __kasan_unpoison_stack(struct task_struct *task, void *sp)
+static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
 {
        void *base = task_stack_page(task);
        size_t size = sp - base;
@@ -77,9 +78,24 @@ void kasan_unpoison_task_stack(struct task_struct *task)
 }
 
 /* Unpoison the stack for the current task beyond a watermark sp value. */
-asmlinkage void kasan_unpoison_remaining_stack(void *sp)
+asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
 {
-       __kasan_unpoison_stack(current, sp);
+       __kasan_unpoison_stack(current, watermark);
+}
+
+/*
+ * Clear all poison for the region between the current SP and a provided
+ * watermark value, as is sometimes required prior to hand-crafted asm function
+ * returns in the middle of functions.
+ */
+void kasan_unpoison_stack_above_sp_to(const void *watermark)
+{
+       const void *sp = __builtin_frame_address(0);
+       size_t size = watermark - sp;
+
+       if (WARN_ON(sp > watermark))
+               return;
+       kasan_unpoison_shadow(sp, size);
 }
 
 /*