[PATCH v4 1/2] kasan: detect negative size in memory operation function
From: Walter Wu
Date: Tue Nov 12 2019 - 01:53:19 EST
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
Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
include/linux/kasan.h | 2 +-
mm/kasan/common.c | 25 ++++++++++++++++++-------
mm/kasan/generic.c | 9 +++++----
mm/kasan/generic_report.c | 11 +++++++++++
mm/kasan/kasan.h | 2 +-
mm/kasan/report.c | 5 +----
mm/kasan/tags.c | 9 +++++----
mm/kasan/tags_report.c | 11 +++++++++++
8 files changed, 53 insertions(+), 21 deletions(-)
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index cc8a03cc9674..2ef6b8fc63ef 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -180,7 +180,7 @@ 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 6814d6d6a023..4bfce0af881f 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);
}
@@ -627,12 +630,20 @@ void kasan_free_shadow(const struct vm_struct *vm)
}
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();
+ unsigned long flags;
+
+ if (likely(!report_enabled()))
+ return false;
+
+ flags = user_access_save();
__kasan_report(addr, size, is_write, ip);
user_access_restore(flags);
+
+ return true;
}
#ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 616f9dd82d12..56ff8885fe2e 100644
--- 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 36c645939bc9..c82bc3f52c9a 100644
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -107,6 +107,17 @@ 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 35cff6bbb716..afada2ce14bf 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -152,7 +152,7 @@ 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 621782100eaa..c94f8e9c78d4 100644
--- 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 0e987c9ca052..25b7734e7013 100644
--- 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 969ae08f59d7..1d412760551a 100644
--- a/mm/kasan/tags_report.c
+++ b/mm/kasan/tags_report.c
@@ -36,6 +36,17 @@
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";
+
#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
struct kasan_alloc_meta *alloc_meta;
struct kmem_cache *cache;
--
2.18.0