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io_uring: fix blocking inline submission

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commit 976517f162a05f4315b2373fd11585c395506259 upstream.

There is a complaint against sys_io_uring_enter() blocking if it submits
stdin reads. The problem is in __io_file_supports_async(), which
sees that it's a cdev and allows it to be processed inline.

Punt char devices using generic rules of io_file_supports_async(),
including checking for presence of *_iter() versions of rw callbacks.
Apparently, it will affect most of cdevs with some exceptions like
null and zero devices.

Cc: stable@vger.kernel.org
Reported-by: Birk Hirdman <lonjil@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d60270856b8a4560a639ef5f76e55eb563633599.1623236455.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov 2021-06-09 12:07:25 +01:00 committed by Greg Kroah-Hartman
parent c98d9318dc
commit a75457f630
1 changed files with 1 additions and 1 deletions
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2
fs/io_uring.c
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@ -2770,7 +2770,7 @@ static bool io_file_supports_async(struct file *file, int rw)
return true; return true;
return false; return false;
} }
if (S_ISCHR(mode) || S_ISSOCK(mode)) if (S_ISSOCK(mode))
return true; return true;
if (S_ISREG(mode)) { if (S_ISREG(mode)) {
if (io_bdev_nowait(file->f_inode->i_sb->s_bdev) && if (io_bdev_nowait(file->f_inode->i_sb->s_bdev) &&