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/nop.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 io_uring/nop.c (limited to 'io_uring/nop.c') diff --git a/io_uring/nop.c b/io_uring/nop.c new file mode 100644 index 000000000..60ab19604 --- /dev/null +++ b/io_uring/nop.c @@ -0,0 +1,90 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +#include + +#include "io_uring.h" +#include "rsrc.h" +#include "nop.h" + +struct io_nop { + struct file *file; + int result; + int fd; + unsigned int flags; + __u64 extra1; + __u64 extra2; +}; + +#define NOP_FLAGS (IORING_NOP_INJECT_RESULT | IORING_NOP_FIXED_FILE | \ + IORING_NOP_FIXED_BUFFER | IORING_NOP_FILE | \ + IORING_NOP_TW | IORING_NOP_CQE32) + +int io_nop_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_nop *nop = io_kiocb_to_cmd(req, struct io_nop); + + nop->flags = READ_ONCE(sqe->nop_flags); + if (nop->flags & ~NOP_FLAGS) + return -EINVAL; + + if (nop->flags & IORING_NOP_INJECT_RESULT) + nop->result = READ_ONCE(sqe->len); + else + nop->result = 0; + if (nop->flags & IORING_NOP_FILE) + nop->fd = READ_ONCE(sqe->fd); + else + nop->fd = -1; + if (nop->flags & IORING_NOP_FIXED_FILE) + req->flags |= REQ_F_FIXED_FILE; + if (nop->flags & IORING_NOP_FIXED_BUFFER) + req->buf_index = READ_ONCE(sqe->buf_index); + if (nop->flags & IORING_NOP_CQE32) { + struct io_ring_ctx *ctx = req->ctx; + + if (!(ctx->flags & (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED))) + return -EINVAL; + nop->extra1 = READ_ONCE(sqe->off); + nop->extra2 = READ_ONCE(sqe->addr); + } + return 0; +} + +int io_nop(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_nop *nop = io_kiocb_to_cmd(req, struct io_nop); + int ret = nop->result; + + if (nop->flags & IORING_NOP_FILE) { + if (req->flags & REQ_F_FIXED_FILE) + req->file = io_file_get_fixed(req, nop->fd, issue_flags); + else + req->file = io_file_get_normal(req, nop->fd); + if (!req->file) { + ret = -EBADF; + goto done; + } + } + if (nop->flags & IORING_NOP_FIXED_BUFFER) { + if (!io_find_buf_node(req, issue_flags)) + ret = -EFAULT; + } +done: + if (ret < 0) + req_set_fail(req); + if (nop->flags & IORING_NOP_CQE32) + io_req_set_res32(req, ret, 0, nop->extra1, nop->extra2); + else + io_req_set_res(req, ret, 0); + if (nop->flags & IORING_NOP_TW) { + req->io_task_work.func = io_req_task_complete; + io_req_task_work_add(req); + return IOU_ISSUE_SKIP_COMPLETE; + } + return IOU_COMPLETE; +} -- cgit v1.3.1