kasan: detect negative size in memory operation function

Patch series "fix the missing underflow in memory operation function", v4.

The patchset helps to produce a KASAN report when size is negative in
memory operation functions.  It is helpful for programmer to solve an
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/

This patch (of 2):

KASAN missed detecting size is a negative number in memset(), memcpy(),
and memmove(), it will cause out-of-bounds bug.  So needs to be detected
by KASAN.

If size is a negative number, then it has a reason to be defined as
out-of-bounds bug type.  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.

KASAN report is shown below:

 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

[cai@lca.pw: fix -Wdeclaration-after-statement warn]
Link: http://lkml.kernel.org/r/1583509030-27939-1-git-send-email-cai@lca.pw
[peterz@infradead.org: fix objtool warning]
Link: http://lkml.kernel.org/r/20200305095436.GV2596@hirez.programming.kicks-ass.net
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Link: http://lkml.kernel.org/r/20191112065302.7015-1-walter-zh.wu@mediatek.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 5cde9e7..31314ca 100644 (file)
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -190,7 +190,7 @@ void kasan_init_tags(void);
 
 void *kasan_reset_tag(const void *addr);
 
-void kasan_report(unsigned long addr, size_t size,
+bool kasan_report(unsigned long addr, size_t size,
                bool is_write, unsigned long ip);
 
 #else /* CONFIG_KASAN_SW_TAGS */

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 6aa5172..e61b4a4 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -105,7 +105,8 @@ 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);
 }
@@ -114,8 +115,9 @@ 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);
 }
@@ -124,8 +126,9 @@ 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);
 }
@@ -634,12 +637,21 @@ void kasan_free_shadow(const struct vm_struct *vm)
 #endif
 
 extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
+extern bool report_enabled(void);
 
-void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
+bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
 {
        unsigned long flags = user_access_save();
-       __kasan_report(addr, size, is_write, ip);
+       bool ret = false;
+
+       if (likely(report_enabled())) {
+               __kasan_report(addr, size, is_write, ip);
+               ret = true;
+       }
+
        user_access_restore(flags);
+
+       return ret;
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 616f9dd..56ff888 100644 (file)
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -173,17 +173,18 @@ static __always_inline bool check_memory_region_inline(unsigned long addr,
        if (unlikely(size == 0))
                return true;
 
+       if (unlikely(addr + size < addr))
+               return !kasan_report(addr, size, write, ret_ip);
+
        if (unlikely((void *)addr <
                kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
-               kasan_report(addr, size, write, ret_ip);
-               return false;
+               return !kasan_report(addr, size, write, ret_ip);
        }
 
        if (likely(!memory_is_poisoned(addr, size)))
                return true;
 
-       kasan_report(addr, size, write, ret_ip);
-       return false;
+       return !kasan_report(addr, size, write, ret_ip);
 }
 
 bool check_memory_region(unsigned long addr, size_t size, bool write,

diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index 2d97efd..e200acb 100644 (file)
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -110,6 +110,17 @@ 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 a negative number, then it has reason to be
+        * defined as out-of-bounds bug type.
+        *
+        * 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.
+        */
+       if (info->access_addr + info->access_size < info->access_addr)
+               return "out-of-bounds";
+
        if (addr_has_shadow(info->access_addr))
                return get_shadow_bug_type(info);
        return get_wild_bug_type(info);

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 3a08327..e8f3719 100644 (file)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -153,7 +153,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
 void *find_first_bad_addr(void *addr, size_t size);
 const char *get_bug_type(struct kasan_access_info *info);
 
-void kasan_report(unsigned long addr, size_t size,
+bool kasan_report(unsigned long addr, size_t size,
                bool is_write, unsigned long ip);
 void kasan_report_invalid_free(void *object, unsigned long ip);
 

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 5ef9f24..cf5c17d 100644 (file)
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -446,7 +446,7 @@ static void print_shadow_for_address(const void *addr)
        }
 }
 
-static bool report_enabled(void)
+bool report_enabled(void)
 {
        if (current->kasan_depth)
                return false;
@@ -478,9 +478,6 @@ void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned lon
        void *untagged_addr;
        unsigned long flags;
 
-       if (likely(!report_enabled()))
-               return;
-
        disable_trace_on_warning();
 
        tagged_addr = (void *)addr;

diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 0e987c9..25b7734 100644 (file)
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -86,6 +86,9 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
        if (unlikely(size == 0))
                return true;
 
+       if (unlikely(addr + size < addr))
+               return !kasan_report(addr, size, write, ret_ip);
+
        tag = get_tag((const void *)addr);
 
        /*
@@ -111,15 +114,13 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
        untagged_addr = reset_tag((const void *)addr);
        if (unlikely(untagged_addr <
                        kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
-               kasan_report(addr, size, write, ret_ip);
-               return false;
+               return !kasan_report(addr, size, write, ret_ip);
        }
        shadow_first = kasan_mem_to_shadow(untagged_addr);
        shadow_last = kasan_mem_to_shadow(untagged_addr + size - 1);
        for (shadow = shadow_first; shadow <= shadow_last; shadow++) {
                if (*shadow != tag) {
-                       kasan_report(addr, size, write, ret_ip);
-                       return false;
+                       return !kasan_report(addr, size, write, ret_ip);
                }
        }
 

diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
index 969ae08..bee4371 100644 (file)
--- a/mm/kasan/tags_report.c
+++ b/mm/kasan/tags_report.c
@@ -60,6 +60,17 @@ const char *get_bug_type(struct kasan_access_info *info)
        }
 
 #endif
+       /*
+        * If access_size is a negative number, then it has reason to be
+        * defined as out-of-bounds bug type.
+        *
+        * 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.
+        */
+       if (info->access_addr + info->access_size < info->access_addr)
+               return "out-of-bounds";
+
        return "invalid-access";
 }