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@vger.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@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7f10c1653e35933c0f1e Suggested-by: Alice Ryhl aliceryhl@google.com Signed-off-by: Carlos Llamas cmllamas@google.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");