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([2620:10d:c090:400::5:6000]) by smtp.gmail.com with ESMTPSA id m13-20020a633f0d000000b005cd835182c5sm5786363pga.79.2024.02.27.06.32.09 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Feb 2024 06:32:09 -0800 (PST) Message-ID: <0dd1079b-03a4-47ec-866b-73317e7e218a@kernel.dk> Date: Tue, 27 Feb 2024 07:32:08 -0700 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: io-uring From: Jens Axboe Subject: [PATCH v2] io_uring/net: improve the usercopy for sendmsg/recvmsg We're spending a considerable amount of the sendmsg/recvmsg time just copying in the message header. And for provided buffers, the known single entry iovec. Be a bit smarter about it and enable/disable user access around our copying. In a test case that does both sendmsg and recvmsg, the runtime before this change (averaged over multiple runs, very stable times however): Kernel Time Diff ==================================== -git 4720 usec -git+commit 4311 usec -8.7% and looking at a profile diff, we see the following: 0.25% +9.33% [kernel.kallsyms] [k] _copy_from_user 4.47% -3.32% [kernel.kallsyms] [k] __io_msg_copy_hdr.constprop.0 where we drop more than 9% of _copy_from_user() time, and consequently add time to __io_msg_copy_hdr() where the copies are now attributed to, but with a net win of 6%. In comparison, the same test case with send/recv runs in 3745 usec, which is (expectedly) still quite a bit faster. But at least sendmsg/recvmsg is now only ~13% slower, where it was ~21% slower before. Signed-off-by: Jens Axboe --- v2: - add missing access_ok() for the iovec copy - only copy iov->iov_len, we never use iov->iov_base diff --git a/io_uring/net.c b/io_uring/net.c index fcbaeb7cc045..7bba7aa3a014 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -282,12 +282,17 @@ static int __io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg struct user_msghdr msg; int ret; - if (copy_from_user(&msg, sr->umsg, sizeof(*sr->umsg))) + if (!user_access_begin(sr->umsg, sizeof(*sr->umsg))) return -EFAULT; - ret = __copy_msghdr(&iomsg->msg, &msg, addr); - if (ret) - return ret; + ret = -EFAULT; + unsafe_get_user(msg.msg_name, &sr->umsg->msg_name, uaccess_end); + unsafe_get_user(msg.msg_namelen, &sr->umsg->msg_namelen, uaccess_end); + unsafe_get_user(msg.msg_iov, &sr->umsg->msg_iov, uaccess_end); + unsafe_get_user(msg.msg_iovlen, &sr->umsg->msg_iovlen, uaccess_end); + unsafe_get_user(msg.msg_control, &sr->umsg->msg_control, uaccess_end); + unsafe_get_user(msg.msg_controllen, &sr->umsg->msg_controllen, uaccess_end); + msg.msg_flags = 0; if (req->flags & REQ_F_BUFFER_SELECT) { if (msg.msg_iovlen == 0) { @@ -295,11 +300,14 @@ static int __io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg iomsg->fast_iov[0].iov_base = NULL; iomsg->free_iov = NULL; } else if (msg.msg_iovlen > 1) { - return -EINVAL; + ret = -EINVAL; + goto uaccess_end; } else { - if (copy_from_user(iomsg->fast_iov, msg.msg_iov, - sizeof(*msg.msg_iov))) - return -EFAULT; + /* we only need the length for provided buffers */ + if (!access_ok(&msg.msg_iov[0].iov_len, sizeof(__kernel_size_t))) + goto uaccess_end; + unsafe_get_user(iomsg->fast_iov[0].iov_len, + &msg.msg_iov[0].iov_len, uaccess_end); sr->len = iomsg->fast_iov[0].iov_len; iomsg->free_iov = NULL; } @@ -307,10 +315,16 @@ static int __io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg if (ddir == ITER_DEST && req->flags & REQ_F_APOLL_MULTISHOT) { iomsg->namelen = msg.msg_namelen; iomsg->controllen = msg.msg_controllen; - if (io_recvmsg_multishot_overflow(iomsg)) - return -EOVERFLOW; + if (io_recvmsg_multishot_overflow(iomsg)) { + ret = -EOVERFLOW; +uaccess_end: + user_access_end(); + return ret; + } } + user_access_end(); } else { + user_access_end(); iomsg->free_iov = iomsg->fast_iov; ret = __import_iovec(ddir, msg.msg_iov, msg.msg_iovlen, UIO_FASTIOV, &iomsg->free_iov, @@ -319,6 +333,12 @@ static int __io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg ret = 0; } + ret = __copy_msghdr(&iomsg->msg, &msg, addr); + if (!ret) + return 0; + + kfree(iomsg->free_iov); + iomsg->free_iov = NULL; return ret; }