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author | Carlos Llamas <cmllamas@google.com> | 2022-08-29 20:12:48 +0000 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-09-01 16:16:05 +0200 |
commit | 1da52815d5f1b654c89044db0cdc6adce43da1f1 (patch) | |
tree | 684a769c503069b16bea6380e963b895fde53b17 /drivers/android/binder_alloc.c | |
parent | 689a2d9f9332a27b1379ef230396e944f949a72b (diff) | |
download | linux-1da52815d5f1b654c89044db0cdc6adce43da1f1.tar.gz linux-1da52815d5f1b654c89044db0cdc6adce43da1f1.tar.bz2 linux-1da52815d5f1b654c89044db0cdc6adce43da1f1.zip |
binder: fix alloc->vma_vm_mm null-ptr dereference
Syzbot reported a couple issues introduced by commit 44e602b4e52f
("binder_alloc: add missing mmap_lock calls when using the VMA"), in
which we attempt to acquire the mmap_lock when alloc->vma_vm_mm has not
been initialized yet.
This can happen if a binder_proc receives a transaction without having
previously called mmap() to setup the binder_proc->alloc space in [1].
Also, a similar issue occurs via binder_alloc_print_pages() when we try
to dump the debugfs binder stats file in [2].
Sample of syzbot's crash report:
==================================================================
KASAN: null-ptr-deref in range [0x0000000000000128-0x000000000000012f]
CPU: 0 PID: 3755 Comm: syz-executor229 Not tainted 6.0.0-rc1-next-20220819-syzkaller #0
syz-executor229[3755] cmdline: ./syz-executor2294415195
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
RIP: 0010:__lock_acquire+0xd83/0x56d0 kernel/locking/lockdep.c:4923
[...]
Call Trace:
<TASK>
lock_acquire kernel/locking/lockdep.c:5666 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
down_read+0x98/0x450 kernel/locking/rwsem.c:1499
mmap_read_lock include/linux/mmap_lock.h:117 [inline]
binder_alloc_new_buf_locked drivers/android/binder_alloc.c:405 [inline]
binder_alloc_new_buf+0xa5/0x19e0 drivers/android/binder_alloc.c:593
binder_transaction+0x242e/0x9a80 drivers/android/binder.c:3199
binder_thread_write+0x664/0x3220 drivers/android/binder.c:3986
binder_ioctl_write_read drivers/android/binder.c:5036 [inline]
binder_ioctl+0x3470/0x6d00 drivers/android/binder.c:5323
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
[...]
==================================================================
Fix these issues by setting up alloc->vma_vm_mm pointer during open()
and caching directly from current->mm. This guarantees we have a valid
reference to take the mmap_lock during scenarios described above.
[1] https://syzkaller.appspot.com/bug?extid=f7dc54e5be28950ac459
[2] https://syzkaller.appspot.com/bug?extid=a75ebe0452711c9e56d9
Fixes: 44e602b4e52f ("binder_alloc: add missing mmap_lock calls when using the VMA")
Cc: <stable@vger.kernel.org> # v5.15+
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: syzbot+f7dc54e5be28950ac459@syzkaller.appspotmail.com
Reported-by: syzbot+a75ebe0452711c9e56d9@syzkaller.appspotmail.com
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20220829201254.1814484-2-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android/binder_alloc.c')
-rw-r--r-- | drivers/android/binder_alloc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 1014beb12802..a61df6e1103a 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -322,7 +322,6 @@ static inline void binder_alloc_set_vma(struct binder_alloc *alloc, */ if (vma) { vm_start = vma->vm_start; - alloc->vma_vm_mm = vma->vm_mm; mmap_assert_write_locked(alloc->vma_vm_mm); } else { mmap_assert_locked(alloc->vma_vm_mm); @@ -792,7 +791,6 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, binder_insert_free_buffer(alloc, buffer); alloc->free_async_space = alloc->buffer_size / 2; binder_alloc_set_vma(alloc, vma); - mmgrab(alloc->vma_vm_mm); return 0; @@ -1080,6 +1078,8 @@ static struct shrinker binder_shrinker = { void binder_alloc_init(struct binder_alloc *alloc) { alloc->pid = current->group_leader->pid; + alloc->vma_vm_mm = current->mm; + mmgrab(alloc->vma_vm_mm); mutex_init(&alloc->mutex); INIT_LIST_HEAD(&alloc->buffers); } |