| Message ID | 20200706201720.3482959-6-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add seccomp notifier ioctl that enables adding fds | expand |
On Mon, Jul 06, 2020 at 01:17:18PM -0700, Kees Cook wrote: > Expand __receive_fd() with support for replace_fd() for the coming seccomp > "addfd" ioctl(). Add new wrapper receive_fd_replace() for the new behavior > and update existing wrappers to retain old behavior. > > Thanks to Colin Ian King <colin.king@canonical.com> for pointing out an > uninitialized variable exposure in an earlier version of this patch. > > Reviewed-by: Sargun Dhillon <sargun@sargun.me> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- Thanks! (One tiny-nit below.) Acked-by: Christian Brauner <christian.brauner@ubuntu.com> > fs/file.c | 24 ++++++++++++++++++------ > include/linux/file.h | 10 +++++++--- > 2 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/fs/file.c b/fs/file.c > index 0efdcf413210..11313ff36802 100644 > --- a/fs/file.c > +++ b/fs/file.c > @@ -937,6 +937,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > /** > * __receive_fd() - 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: __user pointer to write new fd number to > * @o_flags: the O_* flags to apply to the new fd entry > @@ -950,7 +951,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > * > * Returns newly install fd or -ve on error. > */ > -int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > +int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags) > { > struct socket *sock; > int new_fd; > @@ -960,18 +961,30 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > if (error) > return error; > > - new_fd = get_unused_fd_flags(o_flags); > - if (new_fd < 0) > - return new_fd; > + if (fd < 0) { > + new_fd = get_unused_fd_flags(o_flags); > + if (new_fd < 0) > + return new_fd; > + } else > + new_fd = fd; This is nitpicky but coding style technically wants us to use braces around both branches if one of them requires them. ;) > > if (ufd) { > error = put_user(new_fd, ufd); > if (error) { > - put_unused_fd(new_fd); > + if (fd < 0) > + put_unused_fd(new_fd); > return error; > } > } > > + if (fd < 0) > + fd_install(new_fd, get_file(file)); > + else { > + error = replace_fd(new_fd, file, o_flags); > + if (error) > + return error; > + } > + > /* > * Bump the usage count and install the file. The resulting value of > * "error" is ignored here since we only need to take action when > @@ -982,7 +995,6 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > sock_update_netprioidx(&sock->sk->sk_cgrp_data); > sock_update_classid(&sock->sk->sk_cgrp_data); > } > - fd_install(new_fd, get_file(file)); > return new_fd; > } > > diff --git a/include/linux/file.h b/include/linux/file.h > index d9fee9f5c8da..225982792fa2 100644 > --- a/include/linux/file.h > +++ b/include/linux/file.h > @@ -92,18 +92,22 @@ extern void put_unused_fd(unsigned int fd); > > extern void fd_install(unsigned int fd, struct file *file); > > -extern int __receive_fd(struct file *file, int __user *ufd, > +extern int __receive_fd(int fd, struct file *file, int __user *ufd, > unsigned int o_flags); > static inline int receive_fd_user(struct file *file, int __user *ufd, > unsigned int o_flags) > { > if (ufd == NULL) > return -EFAULT; > - return __receive_fd(file, ufd, o_flags); > + return __receive_fd(-1, file, ufd, o_flags); > } > static inline int receive_fd(struct file *file, unsigned int o_flags) > { > - return __receive_fd(file, NULL, o_flags); > + return __receive_fd(-1, file, NULL, o_flags); > +} > +static inline int receive_fd_replace(int fd, struct file *file, unsigned int o_flags) > +{ > + return __receive_fd(fd, file, NULL, o_flags); > } > > extern void flush_delayed_fput(void); > -- > 2.25.1 >
On Tue, Jul 07, 2020 at 02:38:54PM +0200, Christian Brauner wrote: > On Mon, Jul 06, 2020 at 01:17:18PM -0700, Kees Cook wrote: > > Expand __receive_fd() with support for replace_fd() for the coming seccomp > > "addfd" ioctl(). Add new wrapper receive_fd_replace() for the new behavior > > and update existing wrappers to retain old behavior. > > > > Thanks to Colin Ian King <colin.king@canonical.com> for pointing out an > > uninitialized variable exposure in an earlier version of this patch. > > > > Reviewed-by: Sargun Dhillon <sargun@sargun.me> > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > Thanks! > (One tiny-nit below.) > Acked-by: Christian Brauner <christian.brauner@ubuntu.com> > > > fs/file.c | 24 ++++++++++++++++++------ > > include/linux/file.h | 10 +++++++--- > > 2 files changed, 25 insertions(+), 9 deletions(-) > > > > diff --git a/fs/file.c b/fs/file.c > > index 0efdcf413210..11313ff36802 100644 > > --- a/fs/file.c > > +++ b/fs/file.c > > @@ -937,6 +937,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > > /** > > * __receive_fd() - 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: __user pointer to write new fd number to > > * @o_flags: the O_* flags to apply to the new fd entry > > @@ -950,7 +951,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > > * > > * Returns newly install fd or -ve on error. > > */ > > -int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > > +int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags) > > { > > struct socket *sock; > > int new_fd; > > @@ -960,18 +961,30 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > > if (error) > > return error; > > > > - new_fd = get_unused_fd_flags(o_flags); > > - if (new_fd < 0) > > - return new_fd; > > + if (fd < 0) { > > + new_fd = get_unused_fd_flags(o_flags); > > + if (new_fd < 0) > > + return new_fd; > > + } else > > + new_fd = fd; > > This is nitpicky but coding style technically wants us to use braces > around both branches if one of them requires them. ;) Ah yeah, good point. Fixed. Thanks!
diff --git a/fs/file.c b/fs/file.c index 0efdcf413210..11313ff36802 100644 --- a/fs/file.c +++ b/fs/file.c @@ -937,6 +937,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) /** * __receive_fd() - 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: __user pointer to write new fd number to * @o_flags: the O_* flags to apply to the new fd entry @@ -950,7 +951,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) * * Returns newly install fd or -ve on error. */ -int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) +int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags) { struct socket *sock; int new_fd; @@ -960,18 +961,30 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) if (error) return error; - new_fd = get_unused_fd_flags(o_flags); - if (new_fd < 0) - return new_fd; + if (fd < 0) { + new_fd = get_unused_fd_flags(o_flags); + if (new_fd < 0) + return new_fd; + } else + new_fd = fd; if (ufd) { error = put_user(new_fd, ufd); if (error) { - put_unused_fd(new_fd); + if (fd < 0) + put_unused_fd(new_fd); return error; } } + if (fd < 0) + fd_install(new_fd, get_file(file)); + else { + error = replace_fd(new_fd, file, o_flags); + if (error) + return error; + } + /* * Bump the usage count and install the file. The resulting value of * "error" is ignored here since we only need to take action when @@ -982,7 +995,6 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) sock_update_netprioidx(&sock->sk->sk_cgrp_data); sock_update_classid(&sock->sk->sk_cgrp_data); } - fd_install(new_fd, get_file(file)); return new_fd; } diff --git a/include/linux/file.h b/include/linux/file.h index d9fee9f5c8da..225982792fa2 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -92,18 +92,22 @@ extern void put_unused_fd(unsigned int fd); extern void fd_install(unsigned int fd, struct file *file); -extern int __receive_fd(struct file *file, int __user *ufd, +extern int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags); static inline int receive_fd_user(struct file *file, int __user *ufd, unsigned int o_flags) { if (ufd == NULL) return -EFAULT; - return __receive_fd(file, ufd, o_flags); + return __receive_fd(-1, file, ufd, o_flags); } static inline int receive_fd(struct file *file, unsigned int o_flags) { - return __receive_fd(file, NULL, o_flags); + return __receive_fd(-1, file, NULL, o_flags); +} +static inline int receive_fd_replace(int fd, struct file *file, unsigned int o_flags) +{ + return __receive_fd(fd, file, NULL, o_flags); } extern void flush_delayed_fput(void);