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io_uring: fix not locked access to fixed buf table

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commit 05b538c176 upstream.

We can look inside the fixed buffer table only while holding
->uring_lock, however in some cases we don't do the right async prep for
IORING_OP_{WRITE,READ}_FIXED ending up with NULL req->imu forcing making
an io-wq worker to try to resolve the fixed buffer without proper
locking.

Move req->imu setup into early req init paths, i.e. io_prep_rw(), which
is called unconditionally for rw requests and under uring_lock.

Fixes: 634d00df5e ("io_uring: add full-fledged dynamic buffers support")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov 2022-06-09 08:34:35 +01:00 committed by Greg Kroah-Hartman
parent 5696f7983d
commit ea512d540a
1 changed files with 14 additions and 14 deletions
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28
fs/io_uring.c
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@ -2932,15 +2932,24 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
kiocb->ki_complete = io_complete_rw;
}
/* used for fixed read/write too - just read unconditionally */
req->buf_index = READ_ONCE(sqe->buf_index);
req->imu = NULL;
if (req->opcode == IORING_OP_READ_FIXED ||
req->opcode == IORING_OP_WRITE_FIXED) {
req->imu = NULL;
struct io_ring_ctx *ctx = req->ctx;
u16 index;
if (unlikely(req->buf_index >= ctx->nr_user_bufs))
return -EFAULT;
index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
req->imu = ctx->user_bufs[index];
io_req_set_rsrc_node(req);
}
req->rw.addr = READ_ONCE(sqe->addr);
req->rw.len = READ_ONCE(sqe->len);
req->buf_index = READ_ONCE(sqe->buf_index);
return 0;
}
@ -3066,18 +3075,9 @@ static int __io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter
static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter)
{
struct io_ring_ctx *ctx = req->ctx;
struct io_mapped_ubuf *imu = req->imu;
u16 index, buf_index = req->buf_index;
if (likely(!imu)) {
if (unlikely(buf_index >= ctx->nr_user_bufs))
return -EFAULT;
index = array_index_nospec(buf_index, ctx->nr_user_bufs);
imu = READ_ONCE(ctx->user_bufs[index]);
req->imu = imu;
}
return __io_import_fixed(req, rw, iter, imu);
if (WARN_ON_ONCE(!req->imu))
return -EFAULT;
return __io_import_fixed(req, rw, iter, req->imu);
}
static void io_ring_submit_unlock(struct io_ring_ctx *ctx, bool needs_lock)