diff options
author | Carlos Llamas <[email protected]> | 2023-12-01 17:21:32 +0000 |
---|---|---|
committer | Greg Kroah-Hartman <[email protected]> | 2024-01-25 14:34:29 -0800 |
commit | 252a2a5569eb9f8d16428872cc24dea1ac0bb097 (patch) | |
tree | 2d2e64c98b604cf905e5519c47480afe18462d2b | |
parent | 4404c2b832cf0a842b6e3c63fb5749e97dc618ea (diff) | |
download | linux-252a2a5569eb9f8d16428872cc24dea1ac0bb097.tar.gz |
binder: fix race between mmput() and do_exit()
commit 9a9ab0d963621d9d12199df9817e66982582d5a5 upstream.
Task A calls binder_update_page_range() to allocate and insert pages on
a remote address space from Task B. For this, Task A pins the remote mm
via mmget_not_zero() first. This can race with Task B do_exit() and the
final mmput() refcount decrement will come from Task A.
Task A | Task B
------------------+------------------
mmget_not_zero() |
| do_exit()
| exit_mm()
| mmput()
mmput() |
exit_mmap() |
remove_vma() |
fput() |
In this case, the work of ____fput() from Task B is queued up in Task A
as TWA_RESUME. So in theory, Task A returns to userspace and the cleanup
work gets executed. However, Task A instead sleep, waiting for a reply
from Task B that never comes (it's dead).
This means the binder_deferred_release() is blocked until an unrelated
binder event forces Task A to go back to userspace. All the associated
death notifications will also be delayed until then.
In order to fix this use mmput_async() that will schedule the work in
the corresponding mm->async_put_work WQ instead of Task A.
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Reviewed-by: Alice Ryhl <[email protected]>
Signed-off-by: Carlos Llamas <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[cmllamas: fix trivial conflict with missing d8ed45c5dcd4.]
Signed-off-by: Carlos Llamas <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
-rw-r--r-- | drivers/android/binder_alloc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index b150f4d5ed1eda..b82c6e3bdb992c 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -272,7 +272,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, } if (mm) { up_write(&mm->mmap_sem); - mmput(mm); + mmput_async(mm); } return 0; @@ -305,7 +305,7 @@ err_page_ptr_cleared: err_no_vma: if (mm) { up_write(&mm->mmap_sem); - mmput(mm); + mmput_async(mm); } return vma ? -ENOMEM : -ESRCH; } |