blob: 175dbc128735f35cf6b18aa39e066f4504735917 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
|
From d25d6744c46b8289d61180bafb30f3140fef24a4 Mon Sep 17 00:00:00 2001
From: Liam Howlett <liam.howlett@oracle.com>
Date: Mon, 27 Jun 2022 15:18:59 +0000
Subject: [PATCH 69/73] android: binder: fix lockdep check on clearing vma
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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>
---
drivers/android/binder_alloc.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 7981a2598376..5d437c0c842c 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;
}
--
2.37.3
|