io_uring: kiocb_done() should *not* trust ->ki_pos if ->{read,write}_iter() failed

->ki_pos value is unreliable in such cases.  For an obvious example,
consider O_DSYNC write - we feed the data to page cache and start IO,
then we make sure it's completed.  Update of ->ki_pos is dealt with
by the first part; failure in the second ends up with negative value
returned _and_ ->ki_pos left advanced as if sync had been successful.
In the same situation write(2) does not advance the file position
at all.

Reviewed-by: Christian Brauner <[email protected]>
Reviewed-by: Jens Axboe <[email protected]>
Signed-off-by: Al Viro <[email protected]>

0 files changed, 0 insertions, 0 deletions