[PATCH AUTOSEL 5.4 11/23] tun: honor IOCB_NOWAIT flag

Sasha Levin
2020-12-03T13:34:33Z

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 5aac0390a63b8718237a61dd0d24a29201d1c94a ]

tun only checks the file O_NONBLOCK flag, but it should also be checking
the iocb IOCB_NOWAIT flag. Any fops using ->read/write_iter() should check
both, otherwise it breaks users that correctly expect O_NONBLOCK semantics
if IOCB_NOWAIT is set.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/e9451860-96cc-c7c7-47b8-fe42cadd5f4c@kernel.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/tun.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 46bdd0df2eb8b..e72d273999834 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2028,12 +2028,15 @@ static ssize_t tun_chr_write_iter(struct kiocb *iocb, struct iov_iter *from)
struct tun_file *tfile = file->private_data;
struct tun_struct *tun = tun_get(tfile);
ssize_t result;
+ int noblock = 0;

if (!tun)
return -EBADFD;

- result = tun_get_user(tun, tfile, NULL, from,
- file->f_flags & O_NONBLOCK, false);
+ if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
+ noblock = 1;
+
+ result = tun_get_user(tun, tfile, NULL, from, noblock, false);

tun_put(tun);
return result;
@@ -2254,10 +2257,15 @@ static ssize_t tun_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)
struct tun_file *tfile = file->private_data;
struct tun_struct *tun = tun_get(tfile);
ssize_t len = iov_iter_count(to), ret;
+ int noblock = 0;

if (!tun)
return -EBADFD;
- ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK, NULL);
+
+ if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT))
+ noblock = 1;
+
+ ret = tun_do_read(tun, tfile, to, noblock, NULL);
ret = min_t(ssize_t, ret, len);
if (ret > 0)
iocb->ki_pos = ret;
--
2.27.0