For both pidfd and seccomp, the __user pointer is not used. Update __fd_install_received() to make writing to ufd optional. (ufd itself cannot checked for NULL because this changes the SCM_RIGHTS interface behavior.) In these cases, the new fd needs to be returned on success. Update the existing callers to handle it. Add new wrapper fd_install_received() for pidfd and seccomp that does not use the ufd argument.
Signed-off-by: Kees Cook keescook@chromium.org --- fs/file.c | 26 +++++++++++++++++--------- include/linux/file.h | 10 +++++++--- net/compat.c | 2 +- net/core/scm.c | 2 +- 4 files changed, 26 insertions(+), 14 deletions(-)
diff --git a/fs/file.c b/fs/file.c index fcfddae0d252..14a8ef74efb2 100644 --- a/fs/file.c +++ b/fs/file.c @@ -944,11 +944,14 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) * @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. + * checks and count updates. Optionally writes the fd number to userspace, if + * @ufd_required is true (@ufd cannot just be tested for NULL because NULL may + * actually get passed into SCM_RIGHTS). * - * Returns -ve on error. + * Returns newly install fd or -ve on error. */ -int __fd_install_received(struct file *file, int __user *ufd, unsigned int o_flags) +int __fd_install_received(struct file *file, bool ufd_required, int __user *ufd, + unsigned int o_flags) { struct socket *sock; int new_fd; @@ -962,20 +965,25 @@ int __fd_install_received(struct file *file, int __user *ufd, unsigned int o_fla if (new_fd < 0) return new_fd;
- error = put_user(new_fd, ufd); - if (error) { - put_unused_fd(new_fd); - return error; + if (ufd_required) { + error = put_user(new_fd, ufd); + if (error) { + put_unused_fd(new_fd); + return error; + } }
- /* Bump the usage count and install the file. */ + /* Bump the usage count and install the file. The resulting value of + * "error" is ignored here since we only need to take action when + * the file is a socket and testing "sock" for NULL is sufficient. + */ 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; + return new_fd; }
static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) diff --git a/include/linux/file.h b/include/linux/file.h index fe18a1a0d555..999a2c56db07 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -91,12 +91,16 @@ 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); +extern int __fd_install_received(struct file *file, bool ufd_required, + 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); + return __fd_install_received(file, true, ufd, o_flags); +} +static inline int fd_install_received(struct file *file, unsigned int o_flags) +{ + return __fd_install_received(file, false, NULL, o_flags); }
extern void flush_delayed_fput(void); diff --git a/net/compat.c b/net/compat.c index 94f288e8dac5..71494337cca7 100644 --- a/net/compat.c +++ b/net/compat.c @@ -299,7 +299,7 @@ void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm)
for (i = 0; i < fdmax; i++) { err = fd_install_received_user(scm->fp->fp[i], cmsg_data + i, o_flags); - if (err) + if (err < 0) break; }
diff --git a/net/core/scm.c b/net/core/scm.c index df190f1fdd28..b9a0442ebd26 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -307,7 +307,7 @@ void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
for (i = 0; i < fdmax; i++) { err = fd_install_received_user(scm->fp->fp[i], cmsg_data + i, o_flags); - if (err) + if (err < 0) break; }