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Tue, 14 Jan 2025 09:49:13 -0800 (PST) Received: from localhost ([2a00:79e0:9d:4:f0c9:ad9d:2327:39f5]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436e9d8fd03sm188665915e9.6.2025.01.14.09.49.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jan 2025 09:49:12 -0800 (PST) From: Jann Horn Date: Tue, 14 Jan 2025 18:49:00 +0100 Subject: [PATCH] io_uring/rsrc: require cloned buffers to share accounting contexts Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250114-uring-check-accounting-v1-1-42e4145aa743@google.com> X-B4-Tracking: v=1; b=H4sIAIujhmcC/x2MWwqAIBAArxL7naC96yrRR22rLYGFVgTh3bM+Z 2DmAU+OyUOXPODoYs+bjaDSBHAZrSHBc2TIZFZKpQpxOrZG4EK4ihFxO+3xiSIvK91MrcK8hhj vjjTf/7gfQngBZfYV3mgAAAA= X-Change-ID: 20250114-uring-check-accounting-4356f8b91c37 To: Jens Axboe , Pavel Begunkov , io-uring@vger.kernel.org Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1736876949; l=1948; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=+z7ZnXqzo+JwTlyzEMh+aCsl6hsl7DxqJLFJMsWnKp0=; b=rT6imj0L69M67jWPfzUa4j3r15LHqo9N/M1tgoPDIYs3PyYjjQaqkzUMEUM0rjLK+d71yUF7K VfBwaaiceztBH5kuBGGFABgLUxRisIXDO9iYv6BJm4AvG3e4CrZlc3M X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= When IORING_REGISTER_CLONE_BUFFERS is used to clone buffers from uring instance A to uring instance B, where A and B use different MMs for accounting, the accounting can go wrong: If uring instance A is closed before uring instance B, the pinned memory counters for uring instance B will be decremented, even though the pinned memory was originally accounted through uring instance A; so the MM of uring instance B can end up with negative locked memory. Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/r/CAG48ez1zez4bdhmeGLEFxtbFADY4Czn3CV0u9d_T= McbvRA01bg@mail.gmail.com Fixes: 7cc2a6eadcd7 ("io_uring: add IORING_REGISTER_COPY_BUFFERS method") Signed-off-by: Jann Horn --- To be clear, I think this is a very minor issue, feel free to take your time landing it. I put a stable marker on this, but I'm ambivalent about whether this issue even warrants landing a fix in stable - feel free to remove the Cc stable marker if you think it's unnecessary. --- io_uring/rsrc.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index 077f84684c18a0b3f5e622adb4978b6a00353b2f..caecc18dd5be03054ae46179bc0= 918887bf609a4 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -931,6 +931,13 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, s= truct io_ring_ctx *src_ctx int i, ret, off, nr; unsigned int nbufs; =20 + /* + * Accounting state is shared between the two rings; that only works if + * both rings are accounted towards the same counters. + */ + if (ctx->user !=3D src_ctx->user || ctx->mm_account !=3D src_ctx->mm_acco= unt) + return -EINVAL; + /* if offsets are given, must have nr specified too */ if (!arg->nr && (arg->dst_off || arg->src_off)) return -EINVAL; --- base-commit: c45323b7560ec87c37c729b703c86ee65f136d75 change-id: 20250114-uring-check-accounting-4356f8b91c37 --=20 Jann Horn