linux-kernel - [PATCH v2] binder: fix memory leaks of spam and pending work

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Message-ID: <20230922175138.230331-1-cmllamas@google.com>
Date:   Fri, 22 Sep 2023 17:51:37 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Arve Hjønnevåg" <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <brauner@...nel.org>,
        Carlos Llamas <cmllamas@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Li Li <dualli@...gle.com>, Hang Lu <hangl@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        syzkaller-bugs@...glegroups.com, stable@...r.kernel.org,
        syzbot+7f10c1653e35933c0f1e@...kaller.appspotmail.com,
        Alice Ryhl <aliceryhl@...gle.com>, Todd Kjos <tkjos@...gle.com>
Subject: [PATCH v2] binder: fix memory leaks of spam and pending work

A transaction complete work is allocated and queued for each
transaction. Under certain conditions the work->type might be marked as
BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT to notify userspace about
potential spamming threads or as BINDER_WORK_TRANSACTION_PENDING when
the target is currently frozen.

However, these work types are not being handled in binder_release_work()
so they will leak during a cleanup. This was reported by syzkaller with
the following kmemleak dump:

BUG: memory leak
unreferenced object 0xffff88810e2d6de0 (size 32):
  comm "syz-executor338", pid 5046, jiffies 4294968230 (age 13.590s)
  hex dump (first 32 bytes):
    e0 6d 2d 0e 81 88 ff ff e0 6d 2d 0e 81 88 ff ff  .m-......m-.....
    04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81573b75>] kmalloc_trace+0x25/0x90 mm/slab_common.c:1114
    [<ffffffff83d41873>] kmalloc include/linux/slab.h:599 [inline]
    [<ffffffff83d41873>] kzalloc include/linux/slab.h:720 [inline]
    [<ffffffff83d41873>] binder_transaction+0x573/0x4050 drivers/android/binder.c:3152
    [<ffffffff83d45a05>] binder_thread_write+0x6b5/0x1860 drivers/android/binder.c:4010
    [<ffffffff83d486dc>] binder_ioctl_write_read drivers/android/binder.c:5066 [inline]
    [<ffffffff83d486dc>] binder_ioctl+0x1b2c/0x3cf0 drivers/android/binder.c:5352
    [<ffffffff816b25f2>] vfs_ioctl fs/ioctl.c:51 [inline]
    [<ffffffff816b25f2>] __do_sys_ioctl fs/ioctl.c:871 [inline]
    [<ffffffff816b25f2>] __se_sys_ioctl fs/ioctl.c:857 [inline]
    [<ffffffff816b25f2>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:857
    [<ffffffff84b30008>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff84b30008>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fix the leaks by kfreeing these work types in binder_release_work() and
handle them as a BINDER_WORK_TRANSACTION_COMPLETE cleanup.

Cc: stable@...r.kernel.org
Fixes: 0567461a7a6e ("binder: return pending info for frozen async txns")
Fixes: a7dc1e6f99df ("binder: tell userspace to dump current backtrace when detected oneway spamming")
Reported-by: syzbot+7f10c1653e35933c0f1e@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7f10c1653e35933c0f1e
Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
v2 - Handle also peding work and merge with transaction complete as
     suggested by Alice Ryhl. Add corresponding new tags.
v1 - https://lore.kernel.org/all/20230922044241.322832-1-cmllamas@google.com/
---
 drivers/android/binder.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 367afac5f1bf..92128aae2d06 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4812,6 +4812,8 @@ static void binder_release_work(struct binder_proc *proc,
 				"undelivered TRANSACTION_ERROR: %u\n",
 				e->cmd);
 		} break;
+		case BINDER_WORK_TRANSACTION_PENDING:
+		case BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT:
 		case BINDER_WORK_TRANSACTION_COMPLETE: {
 			binder_debug(BINDER_DEBUG_DEAD_TRANSACTION,
 				"undelivered TRANSACTION_COMPLETE\n");
-- 
2.42.0.515.g380fc7ccd1-goog