6.1-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
commit e33ac68e5e21ec1292490dfe061e75c0dbdd3bd4 upstream.
BUG: KASAN: slab-use-after-free in __lock_acquire+0x370b/0x4a10 kernel/locking/lockdep.c:5089 Call Trace: <TASK> ... _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162 class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline] try_to_wake_up+0xb5/0x23c0 kernel/sched/core.c:4205 io_sq_thread_park+0xac/0xe0 io_uring/sqpoll.c:55 io_sq_thread_finish+0x6b/0x310 io_uring/sqpoll.c:96 io_sq_offload_create+0x162/0x11d0 io_uring/sqpoll.c:497 io_uring_create io_uring/io_uring.c:3724 [inline] io_uring_setup+0x1728/0x3230 io_uring/io_uring.c:3806 ...
Kun Hu reports that the SQPOLL creating error path has UAF, which happens if io_uring_alloc_task_context() fails and then io_sq_thread() manages to run and complete before the rest of error handling code, which means io_sq_thread_finish() is looking at already killed task.
Note that this is mostly theoretical, requiring fault injection on the allocation side to trigger in practice.
Cc: stable@vger.kernel.org Reported-by: Kun Hu huk23@m.fudan.edu.cn Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/0f2f1aa5729332612bd01fe0f2f385fd1f06ce7c.173523171... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/sqpoll.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/io_uring/sqpoll.c +++ b/io_uring/sqpoll.c @@ -345,6 +345,7 @@ int io_sqpoll_wait_sq(struct io_ring_ctx __cold int io_sq_offload_create(struct io_ring_ctx *ctx, struct io_uring_params *p) { + struct task_struct *task_to_put = NULL; int ret;
/* Retain compatibility with failing for an invalid attach attempt */ @@ -425,6 +426,7 @@ __cold int io_sq_offload_create(struct i }
sqd->thread = tsk; + task_to_put = get_task_struct(tsk); ret = io_uring_alloc_task_context(tsk, ctx); wake_up_new_task(tsk); if (ret) @@ -435,11 +437,15 @@ __cold int io_sq_offload_create(struct i goto err; }
+ if (task_to_put) + put_task_struct(task_to_put); return 0; err_sqpoll: complete(&ctx->sq_data->exited); err: io_sq_thread_finish(ctx); + if (task_to_put) + put_task_struct(task_to_put); return ret; }