net: rds: fix MR cleanup on copy error

net: rds: fix MR cleanup on copy error

__rds_rdma_map() hands sg/pages ownership to the transport after
get_mr() succeeds. If copying the generated cookie back to user space
fails after that point, the error path must not free those resources
again before dropping the MR reference.

Remove the duplicate unpin/free from the put_user() failure branch so
that MR teardown is handled only through the existing final cleanup
path.

Fixes: 0d4597c8c5ab ("net/rds: Track user mapped pages through special API")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Ao Zhou <draw51280@163.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Reviewed-by: Allison Henderson <achender@kernel.org>
Link: https://patch.msgid.link/79c8ef73ec8e5844d71038983940cc2943099baf.1776764247.git.draw51280@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>