From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- io_uring/epoll.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 io_uring/epoll.c (limited to 'io_uring/epoll.c') diff --git a/io_uring/epoll.c b/io_uring/epoll.c new file mode 100644 index 000000000..b9db8bde2 --- /dev/null +++ b/io_uring/epoll.c @@ -0,0 +1,103 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "io_uring.h" +#include "epoll.h" + +struct io_epoll { + struct file *file; + int epfd; + int op; + int fd; + struct epoll_event event; +}; + +struct io_epoll_wait { + struct file *file; + int maxevents; + struct epoll_event __user *events; +}; + +int io_epoll_ctl_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_epoll *epoll = io_kiocb_to_cmd(req, struct io_epoll); + + if (sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + + epoll->epfd = READ_ONCE(sqe->fd); + epoll->op = READ_ONCE(sqe->len); + epoll->fd = READ_ONCE(sqe->off); + + if (ep_op_has_event(epoll->op)) { + struct epoll_event __user *ev; + + ev = u64_to_user_ptr(READ_ONCE(sqe->addr)); + if (copy_from_user(&epoll->event, ev, sizeof(*ev))) + return -EFAULT; + } + + return 0; +} + +int io_epoll_ctl(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_epoll *ie = io_kiocb_to_cmd(req, struct io_epoll); + bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK; + struct epoll_key key; + int ret; + + CLASS(fd, f)(ie->epfd); + if (fd_empty(f)) + return -EBADF; + + CLASS(fd, tf)(ie->fd); + if (fd_empty(tf)) + return -EBADF; + + key.file = fd_file(tf); + key.fd = ie->fd; + ret = do_epoll_ctl_file(fd_file(f), ie->op, &key, &ie->event, force_nonblock); + if (force_nonblock && ret == -EAGAIN) + return -EAGAIN; + + if (ret < 0) + req_set_fail(req); + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +int io_epoll_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); + + if (sqe->off || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + + iew->maxevents = READ_ONCE(sqe->len); + iew->events = u64_to_user_ptr(READ_ONCE(sqe->addr)); + return 0; +} + +int io_epoll_wait(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); + int ret; + + ret = epoll_sendevents(req->file, iew->events, iew->maxevents); + if (ret == 0) + return -EAGAIN; + if (ret < 0) + req_set_fail(req); + + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} -- cgit v1.3.1