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.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
drivers/android/binder.c | 1 +
fs/io_uring.c | 3 +++
fs/signalfd.c | 1 +
include/linux/fs.h | 1 +
4 files changed, 6 insertions(+)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index b9fb2a926944..c273d0df6939 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -6083,6 +6083,7 @@ 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)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e73969fa96bc..501c7e14c07c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1908,6 +1908,9 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe)
__poll_t mask;
u16 events;
+ if (req->file->f_op->may_pollfree)
+ return -EOPNOTSUPP;
+
if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
return -EINVAL;
if (sqe->addr || sqe->ioprio || sqe->off || sqe->len || sqe->buf_index)
diff --git a/fs/signalfd.c b/fs/signalfd.c
index 3e94d181930f..c3415d969ecf 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -248,6 +248,7 @@ static const struct file_operations signalfd_fops = {
.poll = signalfd_poll,
.read = signalfd_read,
.llseek = noop_llseek,
+ .may_pollfree = true,
};
static int do_signalfd4(int ufd, sigset_t *mask, int flags)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ef118b8ba699..4ecbe12f6215 100644
--- 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 {
--
2.37.2
