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/loop.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 io_uring/loop.c (limited to 'io_uring/loop.c') diff --git a/io_uring/loop.c b/io_uring/loop.c new file mode 100644 index 000000000..bbbb6ef14 --- /dev/null +++ b/io_uring/loop.c @@ -0,0 +1,91 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include "io_uring.h" +#include "wait.h" +#include "loop.h" + +static inline int io_loop_nr_cqes(const struct io_ring_ctx *ctx, + const struct iou_loop_params *lp) +{ + return lp->cq_wait_idx - READ_ONCE(ctx->rings->cq.tail); +} + +static inline void io_loop_wait_start(struct io_ring_ctx *ctx, unsigned nr_wait) +{ + atomic_set(&ctx->cq_wait_nr, nr_wait); + set_current_state(TASK_INTERRUPTIBLE); +} + +static inline void io_loop_wait_finish(struct io_ring_ctx *ctx) +{ + __set_current_state(TASK_RUNNING); + atomic_set(&ctx->cq_wait_nr, IO_CQ_WAKE_INIT); +} + +static void io_loop_wait(struct io_ring_ctx *ctx, struct iou_loop_params *lp, + unsigned nr_wait) +{ + io_loop_wait_start(ctx, nr_wait); + + if (unlikely(io_local_work_pending(ctx) || + io_loop_nr_cqes(ctx, lp) <= 0) || + READ_ONCE(ctx->check_cq)) { + io_loop_wait_finish(ctx); + return; + } + + mutex_unlock(&ctx->uring_lock); + schedule(); + io_loop_wait_finish(ctx); + mutex_lock(&ctx->uring_lock); +} + +static int __io_run_loop(struct io_ring_ctx *ctx) +{ + struct iou_loop_params lp = {}; + + while (true) { + int nr_wait, step_res; + + if (unlikely(!ctx->loop_step)) + return -EFAULT; + + step_res = ctx->loop_step(io_loop_mangle_ctx(ctx), &lp); + if (step_res == IOU_LOOP_STOP) + break; + if (step_res != IOU_LOOP_CONTINUE) + return -EINVAL; + + nr_wait = io_loop_nr_cqes(ctx, &lp); + if (nr_wait > 0) + io_loop_wait(ctx, &lp, nr_wait); + else + nr_wait = 0; + + if (task_work_pending(current)) { + mutex_unlock(&ctx->uring_lock); + io_run_task_work(); + mutex_lock(&ctx->uring_lock); + } + if (unlikely(task_sigpending(current))) + return -EINTR; + io_run_local_work_locked(ctx, nr_wait); + + if (READ_ONCE(ctx->check_cq) & BIT(IO_CHECK_CQ_OVERFLOW_BIT)) + io_cqring_overflow_flush_locked(ctx); + } + + return 0; +} + +int io_run_loop(struct io_ring_ctx *ctx) +{ + int ret; + + if (!io_allowed_run_tw(ctx)) + return -EEXIST; + + mutex_lock(&ctx->uring_lock); + ret = __io_run_loop(ctx); + mutex_unlock(&ctx->uring_lock); + return ret; +} -- cgit v1.3.1