On Mon, Oct 7, 2019 at 10:52 AM Walter Wu [off-list ref] wrote:

On Mon, 2019-10-07 at 10:24 +0200, Dmitry Vyukov wrote:

quoted

On Mon, Oct 7, 2019 at 10:18 AM Walter Wu [off-list ref] wrote:

quoted

The patchsets help to produce KASAN report when size is negative numbers
in memory operation function. It is helpful for programmer to solve the
undefined behavior issue. Patch 1 based on Dmitry's review and
suggestion, patch 2 is a test in order to verify the patch 1.

[1]https://bugzilla.kernel.org/show_bug.cgi?id=199341
[2]https://lore.kernel.org/linux-arm-kernel/20190927034338.15813-1-walter-zh.wu@mediatek.com/ (local)

Walter Wu (2):
kasan: detect invalid size in memory operation function
kasan: add test for invalid size in memmove

 lib/test_kasan.c          | 18 ++++++++++++++++++
 mm/kasan/common.c         | 13 ++++++++-----
 mm/kasan/generic.c        |  5 +++++
 mm/kasan/generic_report.c | 12 ++++++++++++
 mm/kasan/tags.c           |  5 +++++
 mm/kasan/tags_report.c    | 12 ++++++++++++
 6 files changed, 60 insertions(+), 5 deletions(-)




commit 5b3b68660b3d420fd2bd792f2d9fd3ccb8877ef7
Author: Walter-zh Wu [off-list ref]
Date:   Fri Oct 4 18:38:31 2019 +0800

    kasan: detect invalid size in memory operation function

    It is an undefined behavior to pass a negative numbers to
memset()/memcpy()/memmove()
    , so need to be detected by KASAN.

    If size is negative numbers, then it has two reasons to be defined
as out-of-bounds bug type.
    1) Casting negative numbers to size_t would indeed turn up as a
large
    size_t and its value will be larger than ULONG_MAX/2, so that this
can
    qualify as out-of-bounds.
    2) Don't generate new bug type in order to prevent duplicate reports
by
    some systems, e.g. syzbot.

    KASAN report:

     BUG: KASAN: out-of-bounds in kmalloc_memmove_invalid_size+0x70/0xa0
     Read of size 18446744073709551608 at addr ffffff8069660904 by task
cat/72

     CPU: 2 PID: 72 Comm: cat Not tainted
5.4.0-rc1-next-20191004ajb-00001-gdb8af2f372b2-dirty #1
     Hardware name: linux,dummy-virt (DT)
     Call trace:
      dump_backtrace+0x0/0x288
      show_stack+0x14/0x20
      dump_stack+0x10c/0x164
      print_address_description.isra.9+0x68/0x378
      __kasan_report+0x164/0x1a0
      kasan_report+0xc/0x18
      check_memory_region+0x174/0x1d0
      memmove+0x34/0x88
      kmalloc_memmove_invalid_size+0x70/0xa0

    [1] https://bugzilla.kernel.org/show_bug.cgi?id=199341

    Signed-off-by: Walter Wu [off-list ref]
    Reported -by: Dmitry Vyukov [off-list ref]
    Suggested-by: Dmitry Vyukov [off-list ref]

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 6814d6d6a023..6ef0abd27f06 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c

@@ -102,7 +102,8 @@ EXPORT_SYMBOL(__kasan_check_write);
 #undef memset
 void *memset(void *addr, int c, size_t len)
 {
-       check_memory_region((unsigned long)addr, len, true, _RET_IP_);
+       if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_))
+               return NULL;

        return __memset(addr, c, len);
 }

@@ -110,8 +111,9 @@ void *memset(void *addr, int c, size_t len)
 #undef memmove
 void *memmove(void *dest, const void *src, size_t len)
 {
-       check_memory_region((unsigned long)src, len, false, _RET_IP_);
-       check_memory_region((unsigned long)dest, len, true, _RET_IP_);
+       if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
+       !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
+               return NULL;

        return __memmove(dest, src, len);
 }

@@ -119,8 +121,9 @@ void *memmove(void *dest, const void *src, size_t

len)
 #undef memcpy
 void *memcpy(void *dest, const void *src, size_t len)
 {
-       check_memory_region((unsigned long)src, len, false, _RET_IP_);
-       check_memory_region((unsigned long)dest, len, true, _RET_IP_);
+       if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
+       !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
+               return NULL;

        return __memcpy(dest, src, len);
 }

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 616f9dd82d12..02148a317d27 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c

@@ -173,6 +173,11 @@ static __always_inline bool

check_memory_region_inline(unsigned long addr,
        if (unlikely(size == 0))
                return true;

+       if (unlikely((long)size < 0)) {
+               kasan_report(addr, size, write, ret_ip);
+               return false;
+       }
+
        if (unlikely((void *)addr <
                kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
                kasan_report(addr, size, write, ret_ip);

diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index 36c645939bc9..ed0eb94cb811 100644
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c

@@ -107,6 +107,18 @@ static const char *get_wild_bug_type(struct

kasan_access_info *info)

 const char *get_bug_type(struct kasan_access_info *info)
 {
+       /*
+        * If access_size is negative numbers, then it has two reasons
+        * to be defined as out-of-bounds bug type.
+        * 1) Casting negative numbers to size_t would indeed turn up as
+        * a 'large' size_t and its value will be larger than ULONG_MAX/2,
+        * so that this can qualify as out-of-bounds.
+        * 2) Don't generate new bug type in order to prevent duplicate
reports
+        * by some systems, e.g. syzbot.
+        */
+       if ((long)info->access_size < 0)
+               return "out-of-bounds";

"out-of-bounds" is the _least_ frequent KASAN bug type. It won't
prevent duplicates. "heap-out-of-bounds" is the frequent one.

    /*
     * If access_size is negative numbers, then it has two reasons
     * to be defined as out-of-bounds bug type.
     * 1) Casting negative numbers to size_t would indeed turn up as
     * a  "large" size_t and its value will be larger than ULONG_MAX/2,
     *    so that this can qualify as out-of-bounds.
     * 2) Don't generate new bug type in order to prevent duplicate
reports
     *    by some systems, e.g. syzbot. "out-of-bounds" is the _least_
frequent KASAN bug type.
     *    It won't prevent duplicates. "heap-out-of-bounds" is the
frequent one.
     */

We directly add it into the comment.

OK, let's start from the beginning: why do you return "out-of-bounds" here?

quoted

quoted

        if (addr_has_shadow(info->access_addr))
                return get_shadow_bug_type(info);
        return get_wild_bug_type(info);

diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 0e987c9ca052..b829535a3ad7 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c

@@ -86,6 +86,11 @@ bool check_memory_region(unsigned long addr, size_t

size, bool write,
        if (unlikely(size == 0))
                return true;

+       if (unlikely((long)size < 0)) {
+               kasan_report(addr, size, write, ret_ip);
+               return false;
+       }
+
        tag = get_tag((const void *)addr);

        /*

diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
index 969ae08f59d7..012fbe3a793f 100644
--- a/mm/kasan/tags_report.c
+++ b/mm/kasan/tags_report.c

@@ -36,6 +36,18 @@

 const char *get_bug_type(struct kasan_access_info *info)
 {
+       /*
+        * If access_size is negative numbers, then it has two reasons
+        * to be defined as out-of-bounds bug type.
+        * 1) Casting negative numbers to size_t would indeed turn up as
+        * a 'large' size_t and its value will be larger than ULONG_MAX/2,
+        * so that this can qualify as out-of-bounds.
+        * 2) Don't generate new bug type in order to prevent duplicate

reports
+        * by some systems, e.g. syzbot.
+        */
+       if ((long)info->access_size < 0)
+               return "out-of-bounds";
+
 #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
        struct kasan_alloc_meta *alloc_meta;
        struct kmem_cache *cache;








commit fb5cf7bd16e939d1feef229af0211a8616c9ea03
Author: Walter-zh Wu [off-list ref]
Date:   Fri Oct 4 18:32:03 2019 +0800

    kasan: add test for invalid size in memmove

    Test size is negative vaule in memmove in order to verify
    if it correctly get KASAN report.

    Signed-off-by: Walter Wu [off-list ref]

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 49cc4d570a40..06942cf585cc 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c

@@ -283,6 +283,23 @@ static noinline void __init

kmalloc_oob_in_memset(void)
        kfree(ptr);
 }

+static noinline void __init kmalloc_memmove_invalid_size(void)
+{
+       char *ptr;
+       size_t size = 64;
+
+       pr_info("invalid size in memmove\n");
+       ptr = kmalloc(size, GFP_KERNEL);
+       if (!ptr) {
+               pr_err("Allocation failed\n");
+               return;
+       }
+
+       memset((char *)ptr, 0, 64);
+       memmove((char *)ptr, (char *)ptr + 4, -2);
+       kfree(ptr);
+}
+
 static noinline void __init kmalloc_uaf(void)
 {
        char *ptr;

@@ -773,6 +790,7 @@ static int __init kmalloc_tests_init(void)
        kmalloc_oob_memset_4();
        kmalloc_oob_memset_8();
        kmalloc_oob_memset_16();
+       kmalloc_memmove_invalid_size();
        kmalloc_uaf();
        kmalloc_uaf_memset();
        kmalloc_uaf2();




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