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io_uring/kbuf: use READ_ONCE() for userspace-mapped memory 

The struct io_uring_buf elements in a buffer ring are in a memory region
accessible from userspace. A malicious/buggy userspace program could
therefore write to them at any time, so they should be accessed with
READ_ONCE() in the kernel. Commit 98b6fa62c8 ("io_uring/kbuf: always
use READ_ONCE() to read ring provided buffer lengths") already switched
the reads of the len field to READ_ONCE(). Do the same for bid and addr.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Fixes: c7fb19428d ("io_uring: add support for ring mapped supplied buffers")
Cc: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
master
Caleb Sander Mateos 2025-12-04 15:43:31 -07:00 committed by Jens Axboe
parent 525916ce49
commit 78385c7299
1 changed files with 5 additions and 5 deletions
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10
io_uring/kbuf.c
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@ -44,7 +44,7 @@ static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len)
buf_len -= this_len;
/* Stop looping for invalid buffer length of 0 */
if (buf_len || !this_len) {
buf->addr += this_len;
buf->addr = READ_ONCE(buf->addr) + this_len;
buf->len = buf_len;
return false;
}
@ -198,9 +198,9 @@ static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len,
if (*len == 0 || *len > buf_len)
*len = buf_len;
req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;
req->buf_index = buf->bid;
req->buf_index = READ_ONCE(buf->bid);
sel.buf_list = bl;
sel.addr = u64_to_user_ptr(buf->addr);
sel.addr = u64_to_user_ptr(READ_ONCE(buf->addr));
if (io_should_commit(req, issue_flags)) {
io_kbuf_commit(req, sel.buf_list, *len, 1);
@ -280,7 +280,7 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
if (!arg->max_len)
arg->max_len = INT_MAX;
req->buf_index = buf->bid;
req->buf_index = READ_ONCE(buf->bid);
do {
u32 len = READ_ONCE(buf->len);
@ -295,7 +295,7 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
}
}
iov->iov_base = u64_to_user_ptr(buf->addr);
iov->iov_base = u64_to_user_ptr(READ_ONCE(buf->addr));
iov->iov_len = len;
iov++;