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")
Signed-off-by: Todd Kjos <[email protected]>
---
drivers/android/binder.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 9edacc8b9768..fe4c3b49eec1 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1870,7 +1870,7 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
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)) {
@@ -1956,9 +1956,8 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
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.
*/
@@ -3185,6 +3184,7 @@ static void binder_transaction(struct binder_proc *proc,
* 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.
@@ -3194,7 +3194,7 @@ static void binder_transaction(struct binder_proc *proc,
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) {
@@ -3222,7 +3222,7 @@ 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);
}
@@ -3424,7 +3424,7 @@ static int binder_thread_write(struct binder_proc *proc,
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;
}
@@ -4117,7 +4117,7 @@ static int binder_thread_read(struct binder_proc *proc,
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,
--
2.33.0.1079.g6e70778dc9-goog
On Fri, Oct 15, 2021 at 04:38:11PM -0700, Todd Kjos wrote:
> 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")
> Signed-off-by: Todd Kjos <[email protected]>
> ---
Looks good to me.
Acked-by: Christian Brauner <[email protected]>
On Fri, Oct 15, 2021 at 04:38:11PM -0700, Todd Kjos wrote:
> 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.
>
It's really hard for me to understand what this bug looks like to the
user? Is it a memory leak or do we free the wrong thing?
regards,
dan carpenter
On Tue, Nov 2, 2021 at 6:24 AM Dan Carpenter <[email protected]> wrote:
>
> On Fri, Oct 15, 2021 at 04:38:11PM -0700, Todd Kjos wrote:
> > 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.
> >
>
> It's really hard for me to understand what this bug looks like to the
> user? Is it a memory leak or do we free the wrong thing?
It is a difficult case to hit (impossible for "well-behaved"
processes), but it could result in file descriptors being closed when
they shouldn't be.
>
> regards,
> dan carpenter
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
>