From: Pavel Begunkov asml.silence@gmail.com
Older kernels lack io_uring POLLFREE handling. As only affected files are signalfd and android binder the safest option would be to disable polling those files via io_uring and hope there are no users.
Fixes: 221c5eb233823 ("io_uring: add support for IORING_OP_POLL") Signed-off-by: Pavel Begunkov asml.silence@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/binder.c | 1 + fs/io_uring.c | 5 +++++ fs/signalfd.c | 1 + include/linux/fs.h | 1 + 4 files changed, 8 insertions(+)
--- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -6069,6 +6069,7 @@ const struct file_operations binder_fops .open = binder_open, .flush = binder_flush, .release = binder_release, + .may_pollfree = true, };
static int __init init_binder_device(const char *name) --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5198,6 +5198,11 @@ static __poll_t __io_arm_poll_handler(st struct io_ring_ctx *ctx = req->ctx; bool cancel = false;
+ if (req->file->f_op->may_pollfree) { + spin_lock_irq(&ctx->completion_lock); + return -EOPNOTSUPP; + } + INIT_HLIST_NODE(&req->hash_node); io_init_poll_iocb(poll, mask, wake_func); poll->file = req->file; --- a/fs/signalfd.c +++ b/fs/signalfd.c @@ -248,6 +248,7 @@ static const struct file_operations sign .poll = signalfd_poll, .read = signalfd_read, .llseek = noop_llseek, + .may_pollfree = true, };
static int do_signalfd4(int ufd, sigset_t *mask, int flags) --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1859,6 +1859,7 @@ struct file_operations { struct file *file_out, loff_t pos_out, loff_t len, unsigned int remap_flags); int (*fadvise)(struct file *, loff_t, loff_t, int); + bool may_pollfree; } __randomize_layout;
struct inode_operations {