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Wed, 22 Apr 2026 08:54:04 -0700 (PDT) Received: from [192.168.168.223] ([182.176.170.188]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-672c4d50922sm3295274a12.21.2026.04.22.08.54.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 08:54:04 -0700 (PDT) From: Ali Raza Date: Wed, 22 Apr 2026 20:53:05 +0500 Subject: [PATCH] io_uring: fix missing submitter_task ownership check in bpf_io_reg() Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260422-master-v1-1-e82f47558345@gmail.com> X-B4-Tracking: v=1; b=H4sIAODu6GkC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDEyMj3dzE4pLUIt0US7O0VINUi6Qk42QloOKCotS0zAqwQdGxEH5xaVJ WanIJSLdSbS0AA73dz2oAAAA= X-Change-ID: 20260422-master-d96fe0e8bb3c To: Jens Axboe Cc: io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ali Raza , Pavel Begunkov X-Mailer: b4 0.15.2 bpf_io_reg() installs a BPF struct_ops loop_step on any io_uring ring the caller holds a file descriptor for. io_uring_ctx_get_file() only validates that the fd resolves to an io_uring file; it does not verify the caller has authority over the ring's submitter_task. A parallel path in io_uring_register() already enforces this: if (ctx->submitter_task && ctx->submitter_task != current) return -EEXIST; /* register.c:733 */ Without the equivalent check in bpf_io_reg(), a local user with CAP_PERFMON can exploit IORING_SETUP_R_DISABLED -- which defers submitter_task assignment until IORING_REGISTER_ENABLE_RINGS -- to install a loop_step on a ring before a more-privileged process becomes its submitter_task. The loop_step then executes in the privileged process's task context and can issue arbitrary io_uring operations (IORING_OP_WRITE, IORING_OP_READ, IORING_OP_SPLICE) against that process's open file table. This provides a cross-privilege io_uring execution primitive that can serve as a component in a privilege escalation chain when combined with a vector that induces a privileged process to adopt an attacker-controlled ring. Affected: v7.1-rc1+ with CONFIG_IO_URING_BPF_OPS=y. Requires: IORING_SETUP_DEFER_TASKRUN | IORING_SETUP_SINGLE_ISSUER. Add the ownership check in io_install_bpf(), which is called under uring_lock, matching the locking context of the register.c check. Signed-off-by: Ali Raza Cc: Pavel Begunkov --- io_uring/bpf-ops.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/io_uring/bpf-ops.c b/io_uring/bpf-ops.c index 937e48bef40b..cac11c929297 100644 --- a/io_uring/bpf-ops.c +++ b/io_uring/bpf-ops.c @@ -162,6 +162,8 @@ static int io_install_bpf(struct io_ring_ctx *ctx, struct io_uring_bpf_ops *ops) return -EOPNOTSUPP; if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) return -EOPNOTSUPP; + if (ctx->submitter_task && ctx->submitter_task != current) + return -EPERM; if (ctx->bpf_ops) return -EBUSY; --- base-commit: bea8d77e45a8b77f2beca1affc9aa7ed28f39b17 change-id: 20260422-master-d96fe0e8bb3c Best regards, -- Ali Raza