Re: [PATCH] mm: Delay kmemleak object creation of module_alloc()

From: Kefeng Wang
Date: Mon Nov 22 2021 - 07:25:44 EST


On 2021/11/22 20:17, Kefeng Wang wrote:
Yongqiang reports a kmemleak panic when module ismod/rmmod with KASAN
enabled[1] on x86.

The module allocate memory, and it's kmemleak_object is created successfully,
but the KASAN shadow memory of module allocation is not ready, when kmemleak
scan the module's pointer, it will panic due to no shadow memory.

module_alloc
__vmalloc_node_range
kmemleak_vmalloc
kmemleak_scan
update_checksum
kasan_module_alloc
kmemleak_ignore

The bug should exist on ARM64/S390 too, add a VM_DELAY_KMEMLEAK flags, delay
vmalloc'ed object register of kmemleak in module_alloc().

[1] https://lore.kernel.org/all/6d41e2b9-4692-5ec4-b1cd-cbe29ae89739@xxxxxxxxxx/
Reported-by: Yongqiang Liu <liuyongqiang13@xxxxxxxxxx>
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
arch/arm64/kernel/module.c | 4 ++--
arch/s390/kernel/module.c | 5 +++--
arch/x86/kernel/module.c | 7 ++++---
include/linux/kasan.h | 4 ++--
include/linux/vmalloc.h | 7 +++++++
mm/kasan/shadow.c | 9 +++++++--
mm/vmalloc.c | 3 ++-
7 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index b5ec010c481f..e6da010716d0 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -36,7 +36,7 @@ void *module_alloc(unsigned long size)
module_alloc_end = MODULES_END;
p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
- module_alloc_end, gfp_mask, PAGE_KERNEL, 0,
+ module_alloc_end, gfp_mask, PAGE_KERNEL, VM_DELAY_KMEMLEAK,
NUMA_NO_NODE, __builtin_return_address(0));
if (!p && IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
@@ -58,7 +58,7 @@ void *module_alloc(unsigned long size)
PAGE_KERNEL, 0, NUMA_NO_NODE,
__builtin_return_address(0));
- if (p && (kasan_module_alloc(p, size) < 0)) {
+ if (p && (kasan_module_alloc(p, size, gfp_mask) < 0)) {
vfree(p);
return NULL;
}
diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index b01ba460b7ca..8d66a93562ca 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -37,14 +37,15 @@
void *module_alloc(unsigned long size)
{
+ gfp_t gfp_mask = GFP_KERNEL;
void *p;
if (PAGE_ALIGN(size) > MODULES_LEN)
return NULL;
p = __vmalloc_node_range(size, MODULE_ALIGN, MODULES_VADDR, MODULES_END,
- GFP_KERNEL, PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
+ gfp_mask, PAGE_KERNEL_EXEC, VM_DELAY_KMEMLEAK, NUMA_NO_NODE,
__builtin_return_address(0));
- if (p && (kasan_module_alloc(p, size) < 0)) {
+ if (p && (kasan_module_alloc(p, size, gfp_mask) < 0)) {
vfree(p);
return NULL;
}
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 169fb6f4cd2e..ff134d0f1ca1 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -67,6 +67,7 @@ static unsigned long int get_module_load_offset(void)
void *module_alloc(unsigned long size)
{
+ gfp_t gfp_mask = GFP_KERNEL;
void *p;
if (PAGE_ALIGN(size) > MODULES_LEN)
@@ -74,10 +75,10 @@ void *module_alloc(unsigned long size)
p = __vmalloc_node_range(size, MODULE_ALIGN,
MODULES_VADDR + get_module_load_offset(),
- MODULES_END, GFP_KERNEL,
- PAGE_KERNEL, 0, NUMA_NO_NODE,
+ MODULES_END, gfp_mask,
+ PAGE_KERNEL, VM_DELAY_KMEMLEAK, NUMA_NO_NODE,
__builtin_return_address(0));
- if (p && (kasan_module_alloc(p, size) < 0)) {
+ if (p && (kasan_module_alloc(p, size, gfp_mask) < 0)) {
vfree(p);
return NULL;
}
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index d8783b682669..89c99e5e67de 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -474,12 +474,12 @@ static inline void kasan_populate_early_vm_area_shadow(void *start,
* allocations with real shadow memory. With KASAN vmalloc, the special
* case is unnecessary, as the work is handled in the generic case.
*/
-int kasan_module_alloc(void *addr, size_t size);
+int kasan_module_alloc(void *addr, size_t size, gfp_t gfp_mask);
void kasan_free_shadow(const struct vm_struct *vm);
#else /* (CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS) && !CONFIG_KASAN_VMALLOC */
-static inline int kasan_module_alloc(void *addr, size_t size) { return 0; }
+static inline int kasan_module_alloc(void *addr, size_t size, gfp_t gfp_mask) { return 0; }
static inline void kasan_free_shadow(const struct vm_struct *vm) {}
#endif /* (CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS) && !CONFIG_KASAN_VMALLOC */
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 6e022cc712e6..56d2b7828b31 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -28,6 +28,13 @@ struct notifier_block; /* in notifier.h */
#define VM_MAP_PUT_PAGES 0x00000200 /* put pages and free array in vfree */
#define VM_NO_HUGE_VMAP 0x00000400 /* force PAGE_SIZE pte mapping */
+#if defined(CONFIG_KASAN) && (defined(CONFIG_KASAN_GENERIC) || \
+ defined(CONFIG_KASAN_SW_TAGS)) && !defined(CONFIG_KASAN_VMALLOC)
+#define VM_DELAY_KMEMLEAK 0x00000800 /* delay kmemleak object create */
+#else
+#define VM_DELAY_KMEMLEAK 0
+#endif
+
/*
* VM_KASAN is used slightly differently depending on CONFIG_KASAN_VMALLOC.
*
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 4a4929b29a23..6ca43b43419b 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -498,7 +498,7 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
#else /* CONFIG_KASAN_VMALLOC */
-int kasan_module_alloc(void *addr, size_t size)
+int kasan_module_alloc(void *addr, size_t size, gfp_mask)
{
void *ret;
size_t scaled_size;
@@ -520,9 +520,14 @@ int kasan_module_alloc(void *addr, size_t size)
__builtin_return_address(0));
if (ret) {
+ struct vm_struct *vm = find_vm_area(addr);
__memset(ret, KASAN_SHADOW_INIT, shadow_size);
- find_vm_area(addr)->flags |= VM_KASAN;
+ vm->flags |= VM_KASAN;
kmemleak_ignore(ret);
+
+ if (vm->flags | VM_DELAY_KMEMLEAK)

should    if (vm->flags & VM_DELAY_KMEMLEAK),  let's wait more comments, and will update.

+ kmemleak_vmalloc(vm, size, gfp_mask);
+
return 0;
}
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d2a00ad4e1dd..23c595b15839 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3074,7 +3074,8 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
clear_vm_uninitialized_flag(area);
size = PAGE_ALIGN(size);
- kmemleak_vmalloc(area, size, gfp_mask);
+ if (!(vm_flags & VM_DELAY_KMEMLEAK))
+ kmemleak_vmalloc(area, size, gfp_mask);
return addr;