6.17-stable review patch. If anyone has any objections, please let me know.
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From: Caleb Sander Mateos csander@purestorage.com
[ Upstream commit 2f076a453f75de691a081c89bce31b530153d53b ]
io_ring_ctx's enabled with IORING_SETUP_SINGLE_ISSUER are only allowed a single task submitting to the ctx. Although the documentation only mentions this restriction applying to io_uring_enter() syscalls, commit d7cce96c449e ("io_uring: limit registration w/ SINGLE_ISSUER") extends it to io_uring_register(). Ensuring only one task interacts with the io_ring_ctx will be important to allow this task to avoid taking the uring_lock. There is, however, one gap in these checks: io_register_clone_buffers() may take the uring_lock on a second (source) io_ring_ctx, but __io_uring_register() only checks the current thread against the *destination* io_ring_ctx's submitter_task. Fail the IORING_REGISTER_CLONE_BUFFERS with -EEXIST if the source io_ring_ctx has a registered submitter_task other than the current task.
Signed-off-by: Caleb Sander Mateos csander@purestorage.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/rsrc.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index f75f5e43fa4aa..e1e5f0fb0f56d 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -1299,10 +1299,17 @@ int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg) if (src_ctx != ctx) { mutex_unlock(&ctx->uring_lock); lock_two_rings(ctx, src_ctx); + + if (src_ctx->submitter_task && + src_ctx->submitter_task != current) { + ret = -EEXIST; + goto out; + } }
ret = io_clone_buffers(ctx, src_ctx, &buf);
+out: if (src_ctx != ctx) mutex_unlock(&src_ctx->uring_lock);