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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id p14sm3201600pju.7.2020.06.18.13.05.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jun 2020 13:05:15 -0700 (PDT) Date: Thu, 18 Jun 2020 13:05:14 -0700 From: Kees Cook To: Christian Brauner Cc: linux-kernel@vger.kernel.org, Sargun Dhillon , Christian Brauner , "David S. Miller" , Christoph Hellwig , Tycho Andersen , Jakub Kicinski , Alexander Viro , Aleksa Sarai , Matt Denton , Jann Horn , Chris Palmer , Robert Sesek , Giuseppe Scrivano , Greg Kroah-Hartman , Andy Lutomirski , Will Drewry , Shuah Khan , netdev@vger.kernel.org, containers@lists.linux-foundation.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v4 02/11] fs: Move __scm_install_fd() to __fd_install_received() Message-ID: <202006181302.84BFFF52CA@keescook> References: <20200616032524.460144-1-keescook@chromium.org> <20200616032524.460144-3-keescook@chromium.org> <20200618085614.fw3ynalpcipbplf3@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200618085614.fw3ynalpcipbplf3@wittgenstein> Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu, Jun 18, 2020 at 10:56:14AM +0200, Christian Brauner wrote: > On Mon, Jun 15, 2020 at 08:25:15PM -0700, Kees Cook wrote: > > In preparation for users of the "install a received file" logic outside > > of net/ (pidfd and seccomp), relocate and rename __scm_install_fd() from > > net/core/scm.c to __fd_install_received() in fs/file.c, and provide a > > wrapper named fd_install_received_user(), as future patches will change > > the interface to __fd_install_received(). > > > > Signed-off-by: Kees Cook > > --- > > fs/file.c | 47 ++++++++++++++++++++++++++++++++++++++++++++ > > include/linux/file.h | 8 ++++++++ > > include/net/scm.h | 1 - > > net/compat.c | 2 +- > > net/core/scm.c | 32 +----------------------------- > > 5 files changed, 57 insertions(+), 33 deletions(-) > > > > diff --git a/fs/file.c b/fs/file.c > > index abb8b7081d7a..fcfddae0d252 100644 > > --- a/fs/file.c > > +++ b/fs/file.c > > @@ -11,6 +11,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -18,6 +19,8 @@ > > #include > > #include > > #include > > +#include > > +#include > > > > unsigned int sysctl_nr_open __read_mostly = 1024*1024; > > unsigned int sysctl_nr_open_min = BITS_PER_LONG; > > @@ -931,6 +934,50 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > > return err; > > } > > > > +/** > > + * __fd_install_received() - Install received file into file descriptor table > > + * > > + * @fd: fd to install into (if negative, a new fd will be allocated) > > + * @file: struct file that was received from another process > > + * @ufd_required: true to use @ufd for writing fd number to userspace > > + * @ufd: __user pointer to write new fd number to > > + * @o_flags: the O_* flags to apply to the new fd entry > > + * > > + * Installs a received file into the file descriptor table, with appropriate > > + * checks and count updates. Optionally writes the fd number to userspace. > > + * > > + * Returns -ve on error. > > + */ > > +int __fd_install_received(struct file *file, int __user *ufd, unsigned int o_flags) > > +{ > > + struct socket *sock; > > + int new_fd; > > + int error; > > + > > + error = security_file_receive(file); > > + if (error) > > + return error; > > + > > + new_fd = get_unused_fd_flags(o_flags); > > + if (new_fd < 0) > > + return new_fd; > > + > > + error = put_user(new_fd, ufd); > > + if (error) { > > + put_unused_fd(new_fd); > > + return error; > > + } > > + > > + /* Bump the usage count and install the file. */ > > + sock = sock_from_file(file, &error); > > + if (sock) { > > + sock_update_netprioidx(&sock->sk->sk_cgrp_data); > > + sock_update_classid(&sock->sk->sk_cgrp_data); > > + } > > + fd_install(new_fd, get_file(file)); > > + return 0; > > +} > > + > > static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) > > { > > int err = -EBADF; > > diff --git a/include/linux/file.h b/include/linux/file.h > > index 122f80084a3e..fe18a1a0d555 100644 > > --- a/include/linux/file.h > > +++ b/include/linux/file.h > > @@ -91,6 +91,14 @@ extern void put_unused_fd(unsigned int fd); > > > > extern void fd_install(unsigned int fd, struct file *file); > > > > +extern int __fd_install_received(struct file *file, int __user *ufd, > > + unsigned int o_flags); > > +static inline int fd_install_received_user(struct file *file, int __user *ufd, > > + unsigned int o_flags) > > +{ > > + return __fd_install_received(file, ufd, o_flags); > > +} > > Shouldn't this be the other way around such that > fd_install_received_user() is the workhorse that has a "ufd" argument > and fd_install_received() is the static inline function that doesn't? > > extern int fd_install_received_user(struct file *file, int __user *ufd, unsigned int o_flags) > static inline int fd_install_received(struct file *file, unsigned int o_flags) > { > return fd_install_received_user(file, NULL, o_flags); > } So, I think it's all worked out in v5[1], so the helper argument handling is better for the ufd case, as David pointed out earlier. (As in, I think you're reacting to the same general problem here.) > (So I'm on vacation this week some my reviews are selective and spotty > but I promise to be back next week. :)) No worries! -Kees [1] https://lore.kernel.org/lkml/20200617220327.3731559-1-keescook@chromium.org/ -- Kees Cook