From da1b9564e85b1d7baf66cbfabcab27e183a1db63 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Thu, 23 Aug 2018 14:29:56 +0900 Subject: android: binder: fix the race mmap and alloc_new_buf_locked There is RaceFuzzer report like below because we have no lock to close below the race between binder_mmap and binder_alloc_new_buf_locked. To close the race, let's use memory barrier so that if someone see alloc->vma is not NULL, alloc->vma_vm_mm should be never NULL. (I didn't add stable mark intentionallybecause standard android userspace libraries that interact with binder (libbinder & libhwbinder) prevent the mmap/ioctl race. - from Todd) " Thread interleaving: CPU0 (binder_alloc_mmap_handler) CPU1 (binder_alloc_new_buf_locked) ===== ===== // drivers/android/binder_alloc.c // #L718 (v4.18-rc3) alloc->vma = vma; // drivers/android/binder_alloc.c // #L346 (v4.18-rc3) if (alloc->vma == NULL) { ... // alloc->vma is not NULL at this point return ERR_PTR(-ESRCH); } ... // #L438 binder_update_page_range(alloc, 0, (void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr); // In binder_update_page_range() #L218 // But still alloc->vma_vm_mm is NULL here if (need_mm && mmget_not_zero(alloc->vma_vm_mm)) alloc->vma_vm_mm = vma->vm_mm; Crash Log: ================================================================== BUG: KASAN: null-ptr-deref in __atomic_add_unless include/asm-generic/atomic-instrumented.h:89 [inline] BUG: KASAN: null-ptr-deref in atomic_add_unless include/linux/atomic.h:533 [inline] BUG: KASAN: null-ptr-deref in mmget_not_zero include/linux/sched/mm.h:75 [inline] BUG: KASAN: null-ptr-deref in binder_update_page_range+0xece/0x18e0 drivers/android/binder_alloc.c:218 Write of size 4 at addr 0000000000000058 by task syz-executor0/11184 CPU: 1 PID: 11184 Comm: syz-executor0 Not tainted 4.18.0-rc3 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x16e/0x22c lib/dump_stack.c:113 kasan_report_error mm/kasan/report.c:352 [inline] kasan_report+0x163/0x380 mm/kasan/report.c:412 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x140/0x1a0 mm/kasan/kasan.c:267 kasan_check_write+0x14/0x20 mm/kasan/kasan.c:278 __atomic_add_unless include/asm-generic/atomic-instrumented.h:89 [inline] atomic_add_unless include/linux/atomic.h:533 [inline] mmget_not_zero include/linux/sched/mm.h:75 [inline] binder_update_page_range+0xece/0x18e0 drivers/android/binder_alloc.c:218 binder_alloc_new_buf_locked drivers/android/binder_alloc.c:443 [inline] binder_alloc_new_buf+0x467/0xc30 drivers/android/binder_alloc.c:513 binder_transaction+0x125b/0x4fb0 drivers/android/binder.c:2957 binder_thread_write+0xc08/0x2770 drivers/android/binder.c:3528 binder_ioctl_write_read.isra.39+0x24f/0x8e0 drivers/android/binder.c:4456 binder_ioctl+0xa86/0xf34 drivers/android/binder.c:4596 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x154/0xd40 fs/ioctl.c:686 ksys_ioctl+0x94/0xb0 fs/ioctl.c:701 __do_sys_ioctl fs/ioctl.c:708 [inline] __se_sys_ioctl fs/ioctl.c:706 [inline] __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:706 do_syscall_64+0x167/0x4b0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe " Signed-off-by: Todd Kjos Signed-off-by: Minchan Kim Reviewed-by: Martijn Coenen Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 43 ++++++++++++++++++++++++++++++++++-------- 1 file changed, 35 insertions(+), 8 deletions(-) (limited to 'drivers/android') diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 3f3b7b253445..64fd96eada31 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -332,6 +332,35 @@ err_no_vma: return vma ? -ENOMEM : -ESRCH; } + +static inline void binder_alloc_set_vma(struct binder_alloc *alloc, + struct vm_area_struct *vma) +{ + if (vma) + alloc->vma_vm_mm = vma->vm_mm; + /* + * If we see alloc->vma is not NULL, buffer data structures set up + * completely. Look at smp_rmb side binder_alloc_get_vma. + * We also want to guarantee new alloc->vma_vm_mm is always visible + * if alloc->vma is set. + */ + smp_wmb(); + alloc->vma = vma; +} + +static inline struct vm_area_struct *binder_alloc_get_vma( + struct binder_alloc *alloc) +{ + struct vm_area_struct *vma = NULL; + + if (alloc->vma) { + /* Look at description in binder_alloc_set_vma */ + smp_rmb(); + vma = alloc->vma; + } + return vma; +} + static struct binder_buffer *binder_alloc_new_buf_locked( struct binder_alloc *alloc, size_t data_size, @@ -348,7 +377,7 @@ static struct binder_buffer *binder_alloc_new_buf_locked( size_t size, data_offsets_size; int ret; - if (alloc->vma == NULL) { + if (!binder_alloc_get_vma(alloc)) { binder_alloc_debug(BINDER_DEBUG_USER_ERROR, "%d: binder_alloc_buf, no vma\n", alloc->pid); @@ -723,9 +752,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, buffer->free = 1; binder_insert_free_buffer(alloc, buffer); alloc->free_async_space = alloc->buffer_size / 2; - barrier(); - alloc->vma = vma; - alloc->vma_vm_mm = vma->vm_mm; + binder_alloc_set_vma(alloc, vma); mmgrab(alloc->vma_vm_mm); return 0; @@ -754,10 +781,10 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc) int buffers, page_count; struct binder_buffer *buffer; - BUG_ON(alloc->vma); - buffers = 0; mutex_lock(&alloc->mutex); + BUG_ON(alloc->vma); + while ((n = rb_first(&alloc->allocated_buffers))) { buffer = rb_entry(n, struct binder_buffer, rb_node); @@ -900,7 +927,7 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc) */ void binder_alloc_vma_close(struct binder_alloc *alloc) { - WRITE_ONCE(alloc->vma, NULL); + binder_alloc_set_vma(alloc, NULL); } /** @@ -935,7 +962,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item, index = page - alloc->pages; page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE; - vma = alloc->vma; + vma = binder_alloc_get_vma(alloc); if (vma) { if (!mmget_not_zero(alloc->vma_vm_mm)) goto err_mmget; -- cgit v1.2.3-58-ga151