diff options
| author | Liam Howlett <liam.howlett@oracle.com> | 2022-06-27 15:18:59 +0000 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-07-29 18:07:13 -0700 |
| commit | b0cab80ecd54ae3b2356bb081af0bffd538c8265 (patch) | |
| tree | 9e380f660931ff9fe2b9e6aa77e88bb3a5ff4892 /drivers/android | |
| parent | a43cfc87caaf46710c8027a8c23b8a55f1078f19 (diff) | |
android: binder: fix lockdep check on clearing vma
When munmapping a vma, the mmap_lock can be degraded to a write before
calling close() on the file handle. The binder close() function calls
binder_alloc_set_vma() to clear the vma address, which now has a lock dep
check for writing on the mmap_lock. Change the lockdep check to ensure
the reading lock is held while clearing and keep the write check while
writing.
Link: https://lkml.kernel.org/r/20220627151857.2316964-1-Liam.Howlett@oracle.com
Fixes: 472a68df605b ("android: binder: stop saving a pointer to the VMA")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: syzbot+da54fa8d793ca89c741f@syzkaller.appspotmail.com
Acked-by: Todd Kjos <tkjos@google.com>
Cc: "Arve Hjønnevåg" <arve@android.com>
Cc: Christian Brauner (Microsoft) <brauner@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hridya Valsaraju <hridya@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Martijn Coenen <maco@android.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'drivers/android')
| -rw-r--r-- | drivers/android/binder_alloc.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index f555eebceef6..1014beb12802 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -315,12 +315,19 @@ static inline void binder_alloc_set_vma(struct binder_alloc *alloc, { unsigned long vm_start = 0; + /* + * Allow clearing the vma with holding just the read lock to allow + * munmapping downgrade of the write lock before freeing and closing the + * file using binder_alloc_vma_close(). + */ 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); } - mmap_assert_write_locked(alloc->vma_vm_mm); alloc->vma_addr = vm_start; } |