From: Aleix Roca Nonell aleix.rocanonell@bsc.es
commit 99c79f6692ccdc42e04deea8a36e22bb48168a62 upstream.
Commit bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers") introduced an optimization to avoid using the slow iov_iter_advance by manually populating the iov_iter iterator in some cases.
However, the computation of the iterator count field was erroneous: The first bvec was always accounted for an extent of page size even if the bvec length was smaller.
In consequence, some I/O operations on fixed buffers were unable to operate on the full extent of the buffer, consistently skipping some bytes at the end of it.
Fixes: bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers") Cc: stable@vger.kernel.org Signed-off-by: Aleix Roca Nonell aleix.rocanonell@bsc.es Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io_uring.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index 3e887a09533b3..61018559e8fe6 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1032,10 +1032,8 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
iter->bvec = bvec + seg_skip; iter->nr_segs -= seg_skip; - iter->count -= (seg_skip << PAGE_SHIFT); + iter->count -= bvec->bv_len + offset; iter->iov_offset = offset & ~PAGE_MASK; - if (iter->iov_offset) - iter->count -= iter->iov_offset; } }