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([43.132.98.44]) by smtp.googlemail.com with ESMTPSA id gj6-20020a17090b108600b00285a2d14184sm660717pjb.0.2023.11.28.21.35.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Nov 2023 21:35:23 -0800 (PST) From: Hengqi Chen To: linux-kernel@vger.kernel.org Cc: keescook@chromium.org, luto@amacapital.net, wad@chromium.org, alexyonghe@tencent.com, hengqi.chen@gmail.com Subject: [PATCH v3 2/3] seccomp: Introduce new flag SECCOMP_FILTER_FLAG_FILTER_FD Date: Wed, 29 Nov 2023 05:34:39 +0000 Message-Id: <20231129053440.41522-3-hengqi.chen@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231129053440.41522-1-hengqi.chen@gmail.com> References: <20231129053440.41522-1-hengqi.chen@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Tue, 28 Nov 2023 21:35:32 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1783875409110596574 X-GMAIL-MSGID: 1783875409110596574 Add a new flag SECCOMP_FILTER_FLAG_FILTER_FD for SECCOMP_SET_MODE_FILTER. This indicates user supply a seccomp filter fd, not a sock_fprog. It allows us to attach the seccomp filter that is previously loaded via SECCOMP_LOAD_FILTER. Signed-off-by: Hengqi Chen --- include/linux/seccomp.h | 3 ++- include/uapi/linux/seccomp.h | 2 ++ kernel/seccomp.c | 44 +++++++++++++++++++++++++++++++++--- 3 files changed, 45 insertions(+), 4 deletions(-) diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index 175079552f68..3257042c35fc 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -9,7 +9,8 @@ SECCOMP_FILTER_FLAG_SPEC_ALLOW | \ SECCOMP_FILTER_FLAG_NEW_LISTENER | \ SECCOMP_FILTER_FLAG_TSYNC_ESRCH | \ - SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) + SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV | \ + SECCOMP_FILTER_FLAG_FILTER_FD) /* sizeof() the first published struct seccomp_notif_addfd */ #define SECCOMP_NOTIFY_ADDFD_SIZE_VER0 24 diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index ee2c83697810..41e0ca56ef1c 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -26,6 +26,8 @@ #define SECCOMP_FILTER_FLAG_TSYNC_ESRCH (1UL << 4) /* Received notifications wait in killable state (only respond to fatal signals) */ #define SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV (1UL << 5) +/* Indicates that the filter is a fd obtained from SECCOMP_LOAD_FILTER */ +#define SECCOMP_FILTER_FLAG_FILTER_FD (1UL << 6) /* * All BPF programs must return a 32-bit value. diff --git a/kernel/seccomp.c b/kernel/seccomp.c index ef956c3d15c7..a43a6a6b6b77 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -883,8 +883,11 @@ static long seccomp_attach_filter(unsigned int flags, /* Validate resulting filter length. */ total_insns = filter->prog->len; - for (walker = current->seccomp.filter; walker; walker = walker->prev) + for (walker = current->seccomp.filter; walker; walker = walker->prev) { total_insns += walker->prog->len + 4; /* 4 instr penalty */ + if (walker == filter) + return -EEXIST; + } if (total_insns > MAX_INSNS_PER_PATH) return -ENOMEM; @@ -1897,6 +1900,38 @@ static const struct file_operations seccomp_filter_fops = { .release = seccomp_filter_put, }; +/** + * seccomp_prepare_filter_from_fd - prepares filter from a user-supplied fd + * @ufd: pointer to fd that refers to a seccomp filter. + * + * Returns filter on success or an ERR_PTR on failure. + */ +static struct seccomp_filter * +seccomp_prepare_filter_from_fd(const char __user *ufd) +{ + struct seccomp_filter *sfilter; + struct fd f; + int fd; + + if (copy_from_user(&fd, ufd, sizeof(fd))) + return ERR_PTR(-EFAULT); + + f = fdget(fd); + if (!f.file) + return ERR_PTR(-EBADF); + + if (f.file->f_op != &seccomp_filter_fops) { + fdput(f); + return ERR_PTR(-EINVAL); + } + + sfilter = f.file->private_data; + __get_seccomp_filter(sfilter); + + fdput(f); + return sfilter; +} + /** * seccomp_set_mode_filter: internal function for setting seccomp filter * @flags: flags to change filter behavior @@ -1944,7 +1979,10 @@ static long seccomp_set_mode_filter(unsigned int flags, return -EINVAL; /* Prepare the new filter before holding any locks. */ - prepared = seccomp_prepare_user_filter(filter); + if (flags & SECCOMP_FILTER_FLAG_FILTER_FD) + prepared = seccomp_prepare_filter_from_fd(filter); + else + prepared = seccomp_prepare_user_filter(filter); if (IS_ERR(prepared)) return PTR_ERR(prepared); @@ -2005,7 +2043,7 @@ static long seccomp_set_mode_filter(unsigned int flags, } } out_free: - seccomp_filter_free(prepared); + __put_seccomp_filter(prepared); return ret; }