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authorTodd Kjos <tkjos@android.com>2019-06-12 13:29:27 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-13 10:35:55 +0200
commita370003cc301d4361bae20c9ef615f89bf8d1e8a (patch)
treed96c2242a45c688ac249891b7a4d39851a2b2e19
parentb7108486d2d60357dec274276e2f69128f29dcdc (diff)
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binder: fix possible UAF when freeing buffer
There is a race between the binder driver cleaning up a completed transaction via binder_free_transaction() and a user calling binder_ioctl(BC_FREE_BUFFER) to release a buffer. It doesn't matter which is first but they need to be protected against running concurrently which can result in a UAF. Signed-off-by: Todd Kjos <tkjos@google.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/android/binder.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 748ac489ef7e..bc26b5511f0a 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1941,8 +1941,18 @@ static void binder_free_txn_fixups(struct binder_transaction *t)
static void binder_free_transaction(struct binder_transaction *t)
{
- if (t->buffer)
- t->buffer->transaction = NULL;
+ struct binder_proc *target_proc = t->to_proc;
+
+ if (target_proc) {
+ binder_inner_proc_lock(target_proc);
+ if (t->buffer)
+ t->buffer->transaction = NULL;
+ binder_inner_proc_unlock(target_proc);
+ }
+ /*
+ * If the transaction has no target_proc, then
+ * t->buffer->transaction has already been cleared.
+ */
binder_free_txn_fixups(t);
kfree(t);
binder_stats_deleted(BINDER_STAT_TRANSACTION);
@@ -3551,10 +3561,12 @@ err_invalid_target_handle:
static void
binder_free_buf(struct binder_proc *proc, struct binder_buffer *buffer)
{
+ binder_inner_proc_lock(proc);
if (buffer->transaction) {
buffer->transaction->buffer = NULL;
buffer->transaction = NULL;
}
+ binder_inner_proc_unlock(proc);
if (buffer->async_transaction && buffer->target_node) {
struct binder_node *buf_node;
struct binder_work *w;