From: Jens Axboe axboe@kernel.dk
[ Upstream commit 9d8426a09195e2dcf2aa249de2aaadd792d491c7 ]
If we're unlucky with timing, we could be running task_work after having dropped the memory context in the sq thread. Since dropping the context requires a runnable task state, we cannot reliably drop it as part of our check-for-work loop in io_sq_thread(). Instead, abstract out the mm acquire for the sq thread into a helper, and call it from the async task work handler.
Cc: stable@vger.kernel.org # v5.7 Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io_uring.c | 44 +++++++++++++++++++++++++++++--------------- 1 file changed, 29 insertions(+), 15 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4302,6 +4302,28 @@ static void io_async_queue_proc(struct f __io_queue_proc(&pt->req->apoll->poll, pt, head); }
+static void io_sq_thread_drop_mm(struct io_ring_ctx *ctx) +{ + struct mm_struct *mm = current->mm; + + if (mm) { + unuse_mm(mm); + mmput(mm); + } +} + +static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx, + struct io_kiocb *req) +{ + if (io_op_defs[req->opcode].needs_mm && !current->mm) { + if (unlikely(!mmget_not_zero(ctx->sqo_mm))) + return -EFAULT; + use_mm(ctx->sqo_mm); + } + + return 0; +} + static void io_async_task_func(struct callback_head *cb) { struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work); @@ -4333,12 +4355,17 @@ static void io_async_task_func(struct ca if (canceled) { kfree(apoll); io_cqring_ev_posted(ctx); +end_req: req_set_fail_links(req); io_double_put_req(req); return; }
__set_current_state(TASK_RUNNING); + if (io_sq_thread_acquire_mm(ctx, req)) { + io_cqring_add_event(req, -EFAULT); + goto end_req; + } mutex_lock(&ctx->uring_lock); __io_queue_sqe(req, NULL); mutex_unlock(&ctx->uring_lock); @@ -5897,11 +5924,8 @@ static int io_init_req(struct io_ring_ct if (unlikely(req->opcode >= IORING_OP_LAST)) return -EINVAL;
- if (io_op_defs[req->opcode].needs_mm && !current->mm) { - if (unlikely(!mmget_not_zero(ctx->sqo_mm))) - return -EFAULT; - use_mm(ctx->sqo_mm); - } + if (unlikely(io_sq_thread_acquire_mm(ctx, req))) + return -EFAULT;
sqe_flags = READ_ONCE(sqe->flags); /* enforce forwards compatibility on users */ @@ -6011,16 +6035,6 @@ fail_req: return submitted; }
-static inline void io_sq_thread_drop_mm(struct io_ring_ctx *ctx) -{ - struct mm_struct *mm = current->mm; - - if (mm) { - unuse_mm(mm); - mmput(mm); - } -} - static int io_sq_thread(void *data) { struct io_ring_ctx *ctx = data;