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 <tkjos@google.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Martijn Coenen <maco@android.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
da1b9564e8