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/wait.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 io_uring/wait.h (limited to 'io_uring/wait.h') diff --git a/io_uring/wait.h b/io_uring/wait.h new file mode 100644 index 000000000..b7b9c46b1 --- /dev/null +++ b/io_uring/wait.h @@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0 +#ifndef IOU_WAIT_H +#define IOU_WAIT_H + +#include + +/* + * ->cq_wait_nr is armed with the number of lazy task_work adds the waiter + * still needs, and counted down by the add side, with the add reaching zero + * issuing the (single) wake up for this wait cycle. Zero and below means no + * wake up is to be issued: IO_CQ_WAKE_INIT when no task is waiting (also + * what a forced wake up resets it to when claiming one), zero once the + * countdown has fired. + */ +#define IO_CQ_WAKE_INIT (-1) + +struct ext_arg { + size_t argsz; + struct timespec64 ts; + const sigset_t __user *sig; + ktime_t min_time; + bool ts_set; + bool iowait; +}; + +int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags, + struct ext_arg *ext_arg); +int io_run_task_work_sig(struct io_ring_ctx *ctx); +void io_cqring_do_overflow_flush(struct io_ring_ctx *ctx); +void io_cqring_overflow_flush_locked(struct io_ring_ctx *ctx); + +static inline unsigned int __io_cqring_events(struct io_ring_ctx *ctx) +{ + struct io_rings *rings = io_get_rings(ctx); + return ctx->cached_cq_tail - READ_ONCE(rings->cq.head); +} + +static inline unsigned int __io_cqring_events_user(struct io_ring_ctx *ctx) +{ + struct io_rings *rings = io_get_rings(ctx); + + return READ_ONCE(rings->cq.tail) - READ_ONCE(rings->cq.head); +} + +/* + * Reads the tail/head of the CQ ring while providing an acquire ordering, + * see comment at top of io_uring.c. + */ +static inline unsigned io_cqring_events(struct io_ring_ctx *ctx) +{ + smp_rmb(); + return __io_cqring_events(ctx); +} + +#endif -- cgit v1.3.1