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Subject[PATCH 5.10 09/21] binder: dont detect sender/target during buffer cleanup
Date
From: Todd Kjos <tkjos@google.com>

commit 32e9f56a96d8d0f23cb2aeb2a3cd18d40393e787 upstream.

When freeing txn buffers, binder_transaction_buffer_release()
attempts to detect whether the current context is the target by
comparing current->group_leader to proc->tsk. This is an unreliable
test. Instead explicitly pass an 'is_failure' boolean.

Detecting the sender was being used as a way to tell if the
transaction failed to be sent. When cleaning up after
failing to send a transaction, there is no need to close
the fds associated with a BINDER_TYPE_FDA object. Now
'is_failure' can be used to accurately detect this case.

Fixes: 44d8047f1d87 ("binder: use standard functions to allocate fds")
Cc: stable <stable@vger.kernel.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20211015233811.3532235-1-tkjos@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/android/binder.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2254,7 +2254,7 @@ static void binder_transaction_buffer_re
binder_dec_node(buffer->target_node, 1, 0);

off_start_offset = ALIGN(buffer->data_size, sizeof(void *));
- off_end_offset = is_failure ? failed_at :
+ off_end_offset = is_failure && failed_at ? failed_at :
off_start_offset + buffer->offsets_size;
for (buffer_offset = off_start_offset; buffer_offset < off_end_offset;
buffer_offset += sizeof(binder_size_t)) {
@@ -2340,9 +2340,8 @@ static void binder_transaction_buffer_re
binder_size_t fd_buf_size;
binder_size_t num_valid;

- if (proc->tsk != current->group_leader) {
+ if (is_failure) {
/*
- * Nothing to do if running in sender context
* The fd fixups have not been applied so no
* fds need to be closed.
*/
@@ -3544,6 +3543,7 @@ err_invalid_target_handle:
* binder_free_buf() - free the specified buffer
* @proc: binder proc that owns buffer
* @buffer: buffer to be freed
+ * @is_failure: failed to send transaction
*
* If buffer for an async transaction, enqueue the next async
* transaction from the node.
@@ -3553,7 +3553,7 @@ err_invalid_target_handle:
static void
binder_free_buf(struct binder_proc *proc,
struct binder_thread *thread,
- struct binder_buffer *buffer)
+ struct binder_buffer *buffer, bool is_failure)
{
binder_inner_proc_lock(proc);
if (buffer->transaction) {
@@ -3581,7 +3581,7 @@ binder_free_buf(struct binder_proc *proc
binder_node_inner_unlock(buf_node);
}
trace_binder_transaction_buffer_release(buffer);
- binder_transaction_buffer_release(proc, thread, buffer, 0, false);
+ binder_transaction_buffer_release(proc, thread, buffer, 0, is_failure);
binder_alloc_free_buf(&proc->alloc, buffer);
}

@@ -3782,7 +3782,7 @@ static int binder_thread_write(struct bi
proc->pid, thread->pid, (u64)data_ptr,
buffer->debug_id,
buffer->transaction ? "active" : "finished");
- binder_free_buf(proc, thread, buffer);
+ binder_free_buf(proc, thread, buffer, false);
break;
}

@@ -4470,7 +4470,7 @@ retry:
buffer->transaction = NULL;
binder_cleanup_transaction(t, "fd fixups failed",
BR_FAILED_REPLY);
- binder_free_buf(proc, thread, buffer);
+ binder_free_buf(proc, thread, buffer, true);
binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
"%d:%d %stransaction %d fd fixups failed %d/%d, line %d\n",
proc->pid, thread->pid,

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