linux-kernel - [PATCH][next][V2] io_uring: Fix incorrect sizeof operator for copy_from

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Date:   Tue, 15 Jun 2021 14:00:11 +0100
From:   Colin King <colin.king@...onical.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        io-uring@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next][V2] io_uring: Fix incorrect sizeof operator for copy_from_user call

From: Colin Ian King <colin.king@...onical.com>

Static analysis is warning that the sizeof being used is should be
of *data->tags[i] and not data->tags[i]. Although these are the same
size on 64 bit systems it is not a portable assumption to assume
this is true for all cases.  Fix this by using a temporary pointer
tag_slot to make the code a clearer.

Addresses-Coverity: ("Sizeof not portable")
Fixes: d878c81610e1 ("io_uring: hide rsrc tag copy into generic helpers")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
V2: Use temp variable tag_slot, this makes code clearer as suggested by
    Pavel Begunkov.
---
 fs/io_uring.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index d665c9419ad3..7538d0878ff5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7230,8 +7230,10 @@ static int io_rsrc_data_alloc(struct io_ring_ctx *ctx, rsrc_put_fn *do_put,
 	if (utags) {
 		ret = -EFAULT;
 		for (i = 0; i < nr; i++) {
-			if (copy_from_user(io_get_tag_slot(data, i), &utags[i],
-					   sizeof(data->tags[i])))
+			u64 *tag_slot = io_get_tag_slot(data, i);
+
+			if (copy_from_user(tag_slot, &utags[i],
+					   sizeof(*tag_slot)))
 				goto fail;
 		}
 	}
-- 
2.31.1