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16bae3e137
We need to correct some aspects of the IORING_OP_FIXED_FD_INSTALL
command to take into account the security implications of making an
io_uring-private file descriptor generally accessible to a userspace
task.
The first change in this patch is to enable auditing of the FD_INSTALL
operation as installing a file descriptor into a task's file descriptor
table is a security relevant operation and something that admins/users
may want to audit.
The second change is to disable the io_uring credential override
functionality, also known as io_uring "personalities", in the
FD_INSTALL command. The credential override in FD_INSTALL is
particularly problematic as it affects the credentials used in the
security_file_receive() LSM hook. If a task were to request a
credential override via REQ_F_CREDS on a FD_INSTALL operation, the LSM
would incorrectly check to see if the overridden credentials of the
io_uring were able to "receive" the file as opposed to the task's
credentials. After discussions upstream, it's difficult to imagine a
use case where we would want to allow a credential override on a
FD_INSTALL operation so we are simply going to block REQ_F_CREDS on
IORING_OP_FIXED_FD_INSTALL operations.
Fixes: dc18b89ab1
("io_uring/openclose: add support for IORING_OP_FIXED_FD_INSTALL")
Signed-off-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20240123215501.289566-2-paul@paul-moore.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
305 lines
7.3 KiB
C
305 lines
7.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/fsnotify.h>
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#include <linux/namei.h>
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#include <linux/io_uring.h>
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#include <uapi/linux/io_uring.h>
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#include "../fs/internal.h"
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#include "io_uring.h"
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#include "rsrc.h"
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#include "openclose.h"
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struct io_open {
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struct file *file;
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int dfd;
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u32 file_slot;
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struct filename *filename;
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struct open_how how;
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unsigned long nofile;
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};
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struct io_close {
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struct file *file;
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int fd;
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u32 file_slot;
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};
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struct io_fixed_install {
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struct file *file;
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unsigned int o_flags;
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};
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static bool io_openat_force_async(struct io_open *open)
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{
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/*
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* Don't bother trying for O_TRUNC, O_CREAT, or O_TMPFILE open,
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* it'll always -EAGAIN. Note that we test for __O_TMPFILE because
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* O_TMPFILE includes O_DIRECTORY, which isn't a flag we need to force
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* async for.
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*/
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return open->how.flags & (O_TRUNC | O_CREAT | __O_TMPFILE);
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}
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static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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{
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struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
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const char __user *fname;
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int ret;
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if (unlikely(sqe->buf_index))
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return -EINVAL;
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if (unlikely(req->flags & REQ_F_FIXED_FILE))
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return -EBADF;
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/* open.how should be already initialised */
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if (!(open->how.flags & O_PATH) && force_o_largefile())
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open->how.flags |= O_LARGEFILE;
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open->dfd = READ_ONCE(sqe->fd);
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fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
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open->filename = getname(fname);
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if (IS_ERR(open->filename)) {
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ret = PTR_ERR(open->filename);
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open->filename = NULL;
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return ret;
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}
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open->file_slot = READ_ONCE(sqe->file_index);
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if (open->file_slot && (open->how.flags & O_CLOEXEC))
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return -EINVAL;
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open->nofile = rlimit(RLIMIT_NOFILE);
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req->flags |= REQ_F_NEED_CLEANUP;
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if (io_openat_force_async(open))
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req->flags |= REQ_F_FORCE_ASYNC;
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return 0;
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}
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int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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{
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struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
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u64 mode = READ_ONCE(sqe->len);
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u64 flags = READ_ONCE(sqe->open_flags);
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open->how = build_open_how(flags, mode);
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return __io_openat_prep(req, sqe);
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}
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int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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{
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struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
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struct open_how __user *how;
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size_t len;
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int ret;
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how = u64_to_user_ptr(READ_ONCE(sqe->addr2));
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len = READ_ONCE(sqe->len);
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if (len < OPEN_HOW_SIZE_VER0)
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return -EINVAL;
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ret = copy_struct_from_user(&open->how, sizeof(open->how), how, len);
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if (ret)
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return ret;
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return __io_openat_prep(req, sqe);
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}
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int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
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{
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struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
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struct open_flags op;
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struct file *file;
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bool resolve_nonblock, nonblock_set;
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bool fixed = !!open->file_slot;
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int ret;
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ret = build_open_flags(&open->how, &op);
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if (ret)
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goto err;
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nonblock_set = op.open_flag & O_NONBLOCK;
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resolve_nonblock = open->how.resolve & RESOLVE_CACHED;
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if (issue_flags & IO_URING_F_NONBLOCK) {
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WARN_ON_ONCE(io_openat_force_async(open));
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op.lookup_flags |= LOOKUP_CACHED;
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op.open_flag |= O_NONBLOCK;
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}
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if (!fixed) {
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ret = __get_unused_fd_flags(open->how.flags, open->nofile);
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if (ret < 0)
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goto err;
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}
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file = do_filp_open(open->dfd, open->filename, &op);
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if (IS_ERR(file)) {
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/*
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* We could hang on to this 'fd' on retrying, but seems like
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* marginal gain for something that is now known to be a slower
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* path. So just put it, and we'll get a new one when we retry.
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*/
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if (!fixed)
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put_unused_fd(ret);
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ret = PTR_ERR(file);
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/* only retry if RESOLVE_CACHED wasn't already set by application */
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if (ret == -EAGAIN &&
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(!resolve_nonblock && (issue_flags & IO_URING_F_NONBLOCK)))
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return -EAGAIN;
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goto err;
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}
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if ((issue_flags & IO_URING_F_NONBLOCK) && !nonblock_set)
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file->f_flags &= ~O_NONBLOCK;
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if (!fixed)
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fd_install(ret, file);
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else
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ret = io_fixed_fd_install(req, issue_flags, file,
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open->file_slot);
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err:
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putname(open->filename);
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req->flags &= ~REQ_F_NEED_CLEANUP;
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if (ret < 0)
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req_set_fail(req);
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io_req_set_res(req, ret, 0);
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return IOU_OK;
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}
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int io_openat(struct io_kiocb *req, unsigned int issue_flags)
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{
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return io_openat2(req, issue_flags);
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}
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void io_open_cleanup(struct io_kiocb *req)
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{
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struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
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if (open->filename)
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putname(open->filename);
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}
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int __io_close_fixed(struct io_ring_ctx *ctx, unsigned int issue_flags,
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unsigned int offset)
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{
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int ret;
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io_ring_submit_lock(ctx, issue_flags);
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ret = io_fixed_fd_remove(ctx, offset);
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io_ring_submit_unlock(ctx, issue_flags);
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return ret;
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}
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static inline int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags)
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{
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struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
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return __io_close_fixed(req->ctx, issue_flags, close->file_slot - 1);
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}
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int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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{
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struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
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if (sqe->off || sqe->addr || sqe->len || sqe->rw_flags || sqe->buf_index)
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return -EINVAL;
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if (req->flags & REQ_F_FIXED_FILE)
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return -EBADF;
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close->fd = READ_ONCE(sqe->fd);
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close->file_slot = READ_ONCE(sqe->file_index);
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if (close->file_slot && close->fd)
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return -EINVAL;
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return 0;
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}
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int io_close(struct io_kiocb *req, unsigned int issue_flags)
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{
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struct files_struct *files = current->files;
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struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
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struct file *file;
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int ret = -EBADF;
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if (close->file_slot) {
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ret = io_close_fixed(req, issue_flags);
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goto err;
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}
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spin_lock(&files->file_lock);
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file = files_lookup_fd_locked(files, close->fd);
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if (!file || io_is_uring_fops(file)) {
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spin_unlock(&files->file_lock);
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goto err;
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}
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/* if the file has a flush method, be safe and punt to async */
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if (file->f_op->flush && (issue_flags & IO_URING_F_NONBLOCK)) {
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spin_unlock(&files->file_lock);
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return -EAGAIN;
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}
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file = file_close_fd_locked(files, close->fd);
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spin_unlock(&files->file_lock);
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if (!file)
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goto err;
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/* No ->flush() or already async, safely close from here */
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ret = filp_close(file, current->files);
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err:
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if (ret < 0)
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req_set_fail(req);
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io_req_set_res(req, ret, 0);
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return IOU_OK;
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}
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int io_install_fixed_fd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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{
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struct io_fixed_install *ifi;
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unsigned int flags;
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if (sqe->off || sqe->addr || sqe->len || sqe->buf_index ||
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sqe->splice_fd_in || sqe->addr3)
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return -EINVAL;
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/* must be a fixed file */
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if (!(req->flags & REQ_F_FIXED_FILE))
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return -EBADF;
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flags = READ_ONCE(sqe->install_fd_flags);
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if (flags & ~IORING_FIXED_FD_NO_CLOEXEC)
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return -EINVAL;
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/* ensure the task's creds are used when installing/receiving fds */
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if (req->flags & REQ_F_CREDS)
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return -EPERM;
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/* default to O_CLOEXEC, disable if IORING_FIXED_FD_NO_CLOEXEC is set */
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ifi = io_kiocb_to_cmd(req, struct io_fixed_install);
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ifi->o_flags = O_CLOEXEC;
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if (flags & IORING_FIXED_FD_NO_CLOEXEC)
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ifi->o_flags = 0;
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return 0;
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}
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int io_install_fixed_fd(struct io_kiocb *req, unsigned int issue_flags)
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{
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struct io_fixed_install *ifi;
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int ret;
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ifi = io_kiocb_to_cmd(req, struct io_fixed_install);
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ret = receive_fd(req->file, NULL, ifi->o_flags);
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if (ret < 0)
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req_set_fail(req);
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io_req_set_res(req, ret, 0);
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return IOU_OK;
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}
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