From e53759298a7d7e98c3e5c2440d395d19cea7d6bf Mon Sep 17 00:00:00 2001 From: Dylan Yudaken Date: Mon, 6 Nov 2023 20:39:09 +0000 Subject: [PATCH] io_uring: do not clamp read length for multishot read When doing a multishot read, the code path reuses the old read paths. However this breaks an assumption built into those paths, namely that struct io_rw::len is available for reuse by __io_import_iovec. For multishot this results in len being set for the first receive call, and then subsequent calls are clamped to that buffer length incorrectly. Instead keep len as zero after recycling buffers, to reuse the full buffer size of the next selected buffer. Fixes: fc68fcda0491 ("io_uring/rw: add support for IORING_OP_READ_MULTISHOT") Signed-off-by: Dylan Yudaken Link: https://lore.kernel.org/r/20231106203909.197089-4-dyudaken@gmail.com Signed-off-by: Jens Axboe --- io_uring/rw.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/io_uring/rw.c b/io_uring/rw.c index 8321e004ab13..64390d4e20c1 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -912,6 +912,7 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags) int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) { + struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); unsigned int cflags = 0; int ret; @@ -928,7 +929,12 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) * handling arm it. */ if (ret == -EAGAIN) { - io_kbuf_recycle(req, issue_flags); + /* + * Reset rw->len to 0 again to avoid clamping future mshot + * reads, in case the buffer size varies. + */ + if (io_kbuf_recycle(req, issue_flags)) + rw->len = 0; return -EAGAIN; } @@ -941,6 +947,7 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) * jump to the termination path. This request is then done. */ cflags = io_put_kbuf(req, issue_flags); + rw->len = 0; /* similarly to above, reset len to 0 */ if (io_fill_cqe_req_aux(req, issue_flags & IO_URING_F_COMPLETE_DEFER,