Commit 9b47d4ee authored by Andrey Ryabinin's avatar Andrey Ryabinin Committed by Andrew Morton
Browse files

mm/kasan: fix KASAN poisoning in vrealloc() 

A KASAN warning can be triggered when vrealloc() changes the requested
size to a value that is not aligned to KASAN_GRANULE_SIZE.

    ------------[ cut here ]------------
    WARNING: CPU: 2 PID: 1 at mm/kasan/shadow.c:174 kasan_unpoison+0x40/0x48
    ...
    pc : kasan_unpoison+0x40/0x48
    lr : __kasan_unpoison_vmalloc+0x40/0x68
    Call trace:
     kasan_unpoison+0x40/0x48 (P)
     vrealloc_node_align_noprof+0x200/0x320
     bpf_patch_insn_data+0x90/0x2f0
     convert_ctx_accesses+0x8c0/0x1158
     bpf_check+0x1488/0x1900
     bpf_prog_load+0xd20/0x1258
     __sys_bpf+0x96c/0xdf0
     __arm64_sys_bpf+0x50/0xa0
     invoke_syscall+0x90/0x160

Introduce a dedicated kasan_vrealloc() helper that centralizes KASAN
handling for vmalloc reallocations.  The helper accounts for KASAN granule
alignment when growing or shrinking an allocation and ensures that partial
granules are handled correctly.

Use this helper from vrealloc_node_align_noprof() to fix poisoning logic.

[ryabinin.a.a@gmail.com: move kasan_enabled() check, fix build]
  Link: https://lkml.kernel.org/r/20260119144509.32767-1-ryabinin.a.a@gmail.com
Link: https://lkml.kernel.org/r/20260113191516.31015-1-ryabinin.a.a@gmail.com


Fixes: d699440f ("mm: fix vrealloc()'s KASAN poisoning logic")
Signed-off-by: default avatarAndrey Ryabinin <ryabinin.a.a@gmail.com>
Reported-by: default avatarMaciej Żenczykowski <maze@google.com>
Reported-by: default avatar <joonki.min@samsung-slsi.corp-partner.google.com>
Closes: https://lkml.kernel.org/r/CANP3RGeuRW53vukDy7WDO3FiVgu34-xVJYkfpm08oLO3odYFrA@mail.gmail.com


Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Tested-by: default avatarMaciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8a1968bd

include/linux/kasan.h

+14 −0
Original line number Diff line number Diff line
@@ -641,6 +641,17 @@ kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms, 
		__kasan_unpoison_vmap_areas(vms, nr_vms, flags);

}



void __kasan_vrealloc(const void *start, unsigned long old_size,

		unsigned long new_size);



static __always_inline void kasan_vrealloc(const void *start,

					unsigned long old_size,

					unsigned long new_size)

{

	if (kasan_enabled())

		__kasan_vrealloc(start, old_size, new_size);

}



#else /* CONFIG_KASAN_VMALLOC */



static inline void kasan_populate_early_vm_area_shadow(void *start,
@@ -670,6 +681,9 @@ kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms, 
			  kasan_vmalloc_flags_t flags)

{ }



static inline void kasan_vrealloc(const void *start, unsigned long old_size,

				unsigned long new_size) { }



#endif /* CONFIG_KASAN_VMALLOC */



#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \

mm/kasan/common.c

+21 −0
Original line number Diff line number Diff line
@@ -606,4 +606,25 @@ void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms, 
			__kasan_unpoison_vmalloc(addr, size, flags | KASAN_VMALLOC_KEEP_TAG);

	}

}



void __kasan_vrealloc(const void *addr, unsigned long old_size,

		unsigned long new_size)

{

	if (new_size < old_size) {

		kasan_poison_last_granule(addr, new_size);



		new_size = round_up(new_size, KASAN_GRANULE_SIZE);

		old_size = round_up(old_size, KASAN_GRANULE_SIZE);

		if (new_size < old_size)

			__kasan_poison_vmalloc(addr + new_size,

					old_size - new_size);

	} else if (new_size > old_size) {

		old_size = round_down(old_size, KASAN_GRANULE_SIZE);

		__kasan_unpoison_vmalloc(addr + old_size,

					new_size - old_size,

					KASAN_VMALLOC_PROT_NORMAL |

					KASAN_VMALLOC_VM_ALLOC |

					KASAN_VMALLOC_KEEP_TAG);

	}

}

#endif

mm/vmalloc.c

+2 −5
Original line number Diff line number Diff line
@@ -4322,7 +4322,7 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align 
		if (want_init_on_free() || want_init_on_alloc(flags))

			memset((void *)p + size, 0, old_size - size);

		vm->requested_size = size;

		kasan_poison_vmalloc(p + size, old_size - size);

		kasan_vrealloc(p, old_size, size);

		return (void *)p;

	}
@@ -4330,16 +4330,13 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align 
	 * We already have the bytes available in the allocation; use them.

	 */

	if (size <= alloced_size) {

		kasan_unpoison_vmalloc(p + old_size, size - old_size,

				       KASAN_VMALLOC_PROT_NORMAL |

				       KASAN_VMALLOC_VM_ALLOC |

				       KASAN_VMALLOC_KEEP_TAG);

		/*

		 * No need to zero memory here, as unused memory will have

		 * already been zeroed at initial allocation time or during

		 * realloc shrink time.

		 */

		vm->requested_size = size;

		kasan_vrealloc(p, old_size, size);

		return (void *)p;

	}