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 | 5 +++++
fs/signalfd.c | 1 +
include/linux/fs.h | 1 +
4 files changed, 8 insertions(+)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 366b12405708..a5d5247c4f3e 100644
--- 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)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a952288b2ab8..9654b60a06a5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5198,6 +5198,11 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req,
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;
diff --git a/fs/signalfd.c b/fs/signalfd.c
index b94fb5f81797..41dc597b78cc 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 42d246a94228..c8f887641878 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
