From: Alessandro Astone <ales.astone@gmail.com>
To: tkjos@android.com, gregkh@linuxfoundation.org,
brauner@kernel.org, arve@android.com,
linux-kernel@vger.kernel.org, maco@android.com
Cc: Alessandro Astone <ales.astone@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Hridya Valsaraju <hridya@google.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: [PATCH v2 2/2] binder: Gracefully handle BINDER_TYPE_FDA objects with num_fds=0
Date: Fri, 15 Apr 2022 14:00:14 +0200 [thread overview]
Message-ID: <20220415120015.52684-1-ales.astone@gmail.com> (raw)
Some android userspace is sending BINDER_TYPE_FDA objects with
num_fds=0. Like the previous patch, this is reproducible when
playing a video.
Before commit 09184ae9b575 BINDER_TYPE_FDA objects with num_fds=0
were 'correctly handled', as in no fixup was performed.
After commit 09184ae9b575 we aggregate fixup and skip regions in
binder_ptr_fixup structs and distinguish between the two by using
the skip_size field: if it's 0, then it's a fixup, otherwise skip.
When processing BINDER_TYPE_FDA objects with num_fds=0 we add a
skip region of skip_size=0, and this causes issues because now
binder_do_deferred_txn_copies will think this was a fixup region.
To address that, return early from binder_translate_fd_array to
avoid adding an empty skip region.
Fixes: 09184ae9b575 ("binder: defer copies of pre-patched txn data")
Signed-off-by: Alessandro Astone <ales.astone@gmail.com>
---
drivers/android/binder.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 31176edb1069..f3b639e89dd8 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2491,6 +2491,9 @@ static int binder_translate_fd_array(struct list_head *pf_head,
struct binder_proc *proc = thread->proc;
int ret;
+ if (fda->num_fds == 0)
+ return 0;
+
fd_buf_size = sizeof(u32) * fda->num_fds;
if (fda->num_fds >= SIZE_MAX / sizeof(u32)) {
binder_user_error("%d:%d got transaction with invalid number of fds (%lld)\n",
--
2.35.1
next reply other threads:[~2022-04-15 12:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-15 12:00 Alessandro Astone [this message]
2022-04-15 12:00 ` [PATCH v2 1/2] binder: Address corner cases in deferred copy and fixup Alessandro Astone
2022-04-19 18:48 ` Todd Kjos
2022-04-19 18:48 ` [PATCH v2 2/2] binder: Gracefully handle BINDER_TYPE_FDA objects with num_fds=0 Todd Kjos
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