io_uring: fix memory leak of uid in files registration

stable inclusion
from stable-v5.10.110
commit b27de7011cb3ba14b047be2cee0ed8278368665b
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b27de7011cb3ba14b047be2cee0ed8278368665b

--------------------------------

commit c86d18f4 upstream.

When there are no files for __io_sqe_files_scm() to process in the
range, it'll free everything and return. However, it forgets to put uid.

Fixes: 08a45173 ("io_uring: allow sparse fixed file sets")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/accee442376f33ce8aaebb099d04967533efde92.1648226048.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/io_uring.c

@@ -7315,6 +7315,7 @@ static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
 			fput(fpl->fp[i]);
 	} else {
 		kfree_skb(skb);
+		free_uid(fpl->user);
 		kfree(fpl);
 	}