2022-05-17 20:14:16

by Schspa Shi

Subject: [PATCH] binder: fix atomic sleep when get extended error

binder_inner_proc_lock(thread->proc) is a spin lock, copy_to_user can't
be called with in this lock.

Copy it as a local variable, and check the id to make sure the user space
gets the latest error message

Reported-by: [email protected]
Fixes: bd32889e841c ("binder: add BINDER_GET_EXTENDED_ERROR ioctl")
Signed-off-by: Schspa Shi <[email protected]>
---
drivers/android/binder.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index d9253b2a7bd9..5f2e1fa3da74 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5163,13 +5163,20 @@ static int binder_ioctl_get_extended_error(struct binder_thread *thread,
void __user *ubuf)
{
struct binder_extended_error *ee = &thread->ee;
+ struct binder_extended_error eeb;

binder_inner_proc_lock(thread->proc);
- if (copy_to_user(ubuf, ee, sizeof(*ee))) {
- binder_inner_proc_unlock(thread->proc);
+retry:
+ eeb = *ee;
+ binder_inner_proc_unlock(thread->proc);
+ if (copy_to_user(ubuf, &eeb, sizeof(eeb)))
return -EFAULT;
- }

+ binder_inner_proc_lock(thread->proc);
+ if (eeb.id != ee->id) {
+ /* retry to get newest error info */
+ goto retry;
+ }
ee->id = 0;
ee->command = BR_OK;
ee->param = 0;
--
2.24.3 (Apple Git-128)

2022-05-18 01:53:34

by Carlos Llamas

Subject: Re: [PATCH] binder: fix atomic sleep when get extended error

On Wed, May 18, 2022 at 01:52:25AM +0800, Schspa Shi wrote:
> binder_inner_proc_lock(thread->proc) is a spin lock, copy_to_user can't
> be called with in this lock.
>
> Copy it as a local variable, and check the id to make sure the user space
> gets the latest error message
>
> Reported-by: [email protected]
> Fixes: bd32889e841c ("binder: add BINDER_GET_EXTENDED_ERROR ioctl")
> Signed-off-by: Schspa Shi <[email protected]>
> ---
> drivers/android/binder.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index d9253b2a7bd9..5f2e1fa3da74 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -5163,13 +5163,20 @@ static int binder_ioctl_get_extended_error(struct binder_thread *thread,
> void __user *ubuf)
> {
> struct binder_extended_error *ee = &thread->ee;
> + struct binder_extended_error eeb;
>
> binder_inner_proc_lock(thread->proc);
> - if (copy_to_user(ubuf, ee, sizeof(*ee))) {
> - binder_inner_proc_unlock(thread->proc);
> +retry:
> + eeb = *ee;
> + binder_inner_proc_unlock(thread->proc);
> + if (copy_to_user(ubuf, &eeb, sizeof(eeb)))
> return -EFAULT;
> - }
>
> + binder_inner_proc_lock(thread->proc);
> + if (eeb.id != ee->id) {
> + /* retry to get newest error info */
> + goto retry;
> + }
> ee->id = 0;
> ee->command = BR_OK;
> ee->param = 0;
> --
> 2.24.3 (Apple Git-128)
>

Oops! Thank you for your patch. In this case the local copy would be
enough, no need for the retry logic as this is already taken care of.
You could also leverage the binder_set_extended_error() to reset the
thread->ee. Would you mind sending these updates? I was thinking
something like this:

drivers/android/binder.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 83facfa1a5c3..f92021cd384b 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5163,19 +5163,16 @@ static int binder_ioctl_get_freezer_info(
static int binder_ioctl_get_extended_error(struct binder_thread *thread,
void __user *ubuf)
{
- struct binder_extended_error *ee = &thread->ee;
+ struct binder_extended_error ee;

binder_inner_proc_lock(thread->proc);
- if (copy_to_user(ubuf, ee, sizeof(*ee))) {
- binder_inner_proc_unlock(thread->proc);
- return -EFAULT;
- }
-
- ee->id = 0;
- ee->command = BR_OK;
- ee->param = 0;
+ ee = thread->ee;
+ binder_set_extended_error(&thread->ee, 0, BR_OK, 0);
binder_inner_proc_unlock(thread->proc);

+ if (copy_to_user(ubuf, &ee, sizeof(ee)))
+ return -EFAULT;
+
return 0;
}

--

Carlos Llamas

2022-05-18 03:52:08

by Schspa Shi

Subject: Re: [PATCH] binder: fix atomic sleep when get extended error

Carlos Llamas <[email protected]> writes:

> On Wed, May 18, 2022 at 01:52:25AM +0800, Schspa Shi wrote:
>> binder_inner_proc_lock(thread->proc) is a spin lock, copy_to_user can't
>> be called with in this lock.
>>
>> Copy it as a local variable, and check the id to make sure the user space
>> gets the latest error message
>>
>> Reported-by: [email protected]
>> Fixes: bd32889e841c ("binder: add BINDER_GET_EXTENDED_ERROR ioctl")
>> Signed-off-by: Schspa Shi <[email protected]>
>> ---
>> drivers/android/binder.c | 13 ++++++++++---
>> 1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
>> index d9253b2a7bd9..5f2e1fa3da74 100644
>> --- a/drivers/android/binder.c
>> +++ b/drivers/android/binder.c
>> @@ -5163,13 +5163,20 @@ static int binder_ioctl_get_extended_error(struct binder_thread *thread,
>> void __user *ubuf)
>> {
>> struct binder_extended_error *ee = &thread->ee;
>> + struct binder_extended_error eeb;
>>
>> binder_inner_proc_lock(thread->proc);
>> - if (copy_to_user(ubuf, ee, sizeof(*ee))) {
>> - binder_inner_proc_unlock(thread->proc);
>> +retry:
>> + eeb = *ee;
>> + binder_inner_proc_unlock(thread->proc);
>> + if (copy_to_user(ubuf, &eeb, sizeof(eeb)))
>> return -EFAULT;
>> - }
>>
>> + binder_inner_proc_lock(thread->proc);
>> + if (eeb.id != ee->id) {
>> + /* retry to get newest error info */
>> + goto retry;
>> + }
>> ee->id = 0;
>> ee->command = BR_OK;
>> ee->param = 0;
>> --
>> 2.24.3 (Apple Git-128)
>>
>
> Oops! Thank you for your patch. In this case the local copy would be
> enough, no need for the retry logic as this is already taken care of.
> You could also leverage the binder_set_extended_error() to reset the
> thread->ee. Would you mind sending these updates? I was thinking
> something like this:

Yes, I have sent a v2 patch for this, please review it.


>
> drivers/android/binder.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 83facfa1a5c3..f92021cd384b 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -5163,19 +5163,16 @@ static int binder_ioctl_get_freezer_info(
> static int binder_ioctl_get_extended_error(struct binder_thread *thread,
> void __user *ubuf)
> {
> - struct binder_extended_error *ee = &thread->ee;
> + struct binder_extended_error ee;
>
> binder_inner_proc_lock(thread->proc);
> - if (copy_to_user(ubuf, ee, sizeof(*ee))) {
> - binder_inner_proc_unlock(thread->proc);
> - return -EFAULT;
> - }
> -
> - ee->id = 0;
> - ee->command = BR_OK;
> - ee->param = 0;
> + ee = thread->ee;
> + binder_set_extended_error(&thread->ee, 0, BR_OK, 0);
> binder_inner_proc_unlock(thread->proc);
>
> + if (copy_to_user(ubuf, &ee, sizeof(ee)))
> + return -EFAULT;
> +
> return 0;
> }

--
BRs
Schspa Shi