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android: binder: fix lockdep check on clearing vma

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commit b0cab80ecd54ae3b2356bb081af0bffd538c8265 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Liam Howlett 2022-06-27 15:18:59 +00:00 committed by Greg Kroah-Hartman
parent 8a239dd886
commit d25d6744c4
1 changed files with 8 additions and 1 deletions
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9
drivers/android/binder_alloc.c
View File

@ -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;
}