On Wed, Feb 17, 2021 at 08:43:47PM +0600, Sabyrzhan Tasbolatov wrote:
> syzbot found WARNING in iov_iter_revert[1] when iov_iter_count() returns 0,
> therefore INT_MAX is passed to iov_iter_revert() causing > MAX_RW_COUNT
> warning.
>
> static inline ssize_t do_tty_write()
> {
> ..
> size_t count = iov_iter_count(from);
> ..
> size_t size = count;
> if (ret != size)
> iov_iter_revert(from, size-ret);
>
> [1] WARNING: lib/iov_iter.c:1090
> Call Trace:
> do_tty_write drivers/tty/tty_io.c:967 [inline]
> file_tty_write.constprop.0+0x55f/0x8f0 drivers/tty/tty_io.c:1048
> call_write_iter include/linux/fs.h:1901 [inline]
> new_sync_write+0x426/0x650 fs/read_write.c:518
> vfs_write+0x791/0xa30 fs/read_write.c:605
> ksys_write+0x12d/0x250 fs/read_write.c:658
>
> Fixes: 494e63ee9c("tty: implement write_iter")
Nit, you need a ' ' before your '(' character here, otherwise the
linux-next scripts will complain.
> Reported-by: syzbot+3d2c27c2b7dc2a948...@syzkaller.appspotmail.com
> Signed-off-by: Sabyrzhan Tasbolatov <snovit...@gmail.com>
> ---
> drivers/tty/tty_io.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 816e709afa56..8d6d579ecc3b 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -905,6 +905,9 @@ static inline ssize_t do_tty_write(
> ssize_t ret, written = 0;
> unsigned int chunk;
>
> + if (!count)
> + return -EINVAL;
According to the man page for write(2), I think this is the wrong error
value to return, unless that is the value that was returned on kernels
before the commit listed above.
Can you verify this?
thanks,
greg k-h
