Re: [PATCH v4] mm: Defer kmemleak object creation of module_alloc()

From: Andrey Konovalov
Date: Thu Nov 25 2021 - 11:19:50 EST

On Thu, Nov 25, 2021 at 8:52 AM 'Kefeng Wang' via kasan-dev
<kasan-dev@xxxxxxxxxxxxxxxx> wrote:
>
> Yongqiang reports a kmemleak panic when module insmod/rmmod
> with KASAN enabled(without KASAN_VMALLOC) on x86[1].
>
> When the module area allocates memory, it's kmemleak_object
> is created successfully, but the KASAN shadow memory of module
> allocation is not ready, so when kmemleak scan the module's
> pointer, it will panic due to no shadow memory with KASAN check.
>
> module_alloc
> __vmalloc_node_range
> kmemleak_vmalloc
> kmemleak_scan
> update_checksum
> kasan_module_alloc
> kmemleak_ignore
>
> Note, there is no problem if KASAN_VMALLOC enabled, the modules
> area entire shadow memory is preallocated. Thus, the bug only
> exits on ARCH which supports dynamic allocation of module area
> per module load, for now, only x86/arm64/s390 are involved.
>
>
> Add a VM_DEFER_KMEMLEAK flags, defer vmalloc'ed object register
> of kmemleak in module_alloc() to fix this issue.
>
> [1] https://lore.kernel.org/all/6d41e2b9-4692-5ec4-b1cd-cbe29ae89739@xxxxxxxxxx/
>
> Fixes: 793213a82de4 ("s390/kasan: dynamic shadow mem allocation for modules")
> Fixes: 39d114ddc682 ("arm64: add KASAN support")
> Fixes: bebf56a1b176 ("kasan: enable instrumentation of global variables")
> Reported-by: Yongqiang Liu <liuyongqiang13@xxxxxxxxxx>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> ---
> V4:
> - add fix tag
> - fix missing change about VM_DELAY_KMEMLEAK
> v3:
> - update changelog to add more explanation
> - use DEFER instead of DELAY sugguested by Catalin.
> v2:
> - fix type error on changelog and kasan_module_alloc()
>
> 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..309a27553c87 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_DEFER_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..d52d85367bf7 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_DEFER_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..95fa745e310a 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_DEFER_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..506fc6e6a126 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_DEFER_KMEMLEAK 0x00000800 /* defer kmemleak object creation */
> +#else
> +#define VM_DEFER_KMEMLEAK 0
> +#endif

No need for CONFIG_KASAN check: CONFIG_KASAN_GENERIC ||
CONFIG_KASAN_SW_TAGS implies CONFIG_KASAN.



> +
> /*
> * 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..2ade2f484562 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_t 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_DEFER_KMEMLEAK)
> + kmemleak_vmalloc(vm, size, gfp_mask);
> +
> return 0;
> }
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index d2a00ad4e1dd..bf3c2fe8f528 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_DEFER_KMEMLEAK))
> + kmemleak_vmalloc(area, size, gfp_mask);
>
> return addr;
>
> --
> 2.26.2
>
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