The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 19d340a2988d4f3e673cded9dde405d727d7e248 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025013011-scenic-crazed-e3c8@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 19d340a2988d4f3e673cded9dde405d727d7e248 Mon Sep 17 00:00:00 2001 From: Jann Horn jannh@google.com Date: Tue, 14 Jan 2025 18:49:00 +0100 Subject: [PATCH] io_uring/rsrc: require cloned buffers to share accounting contexts

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_TMcbvRA01b... Fixes: 7cc2a6eadcd7 ("io_uring: add IORING_REGISTER_COPY_BUFFERS method") Signed-off-by: Jann Horn jannh@google.com Link: https://lore.kernel.org/r/20250114-uring-check-accounting-v1-1-42e4145aa743@... Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index 964a47c8d85e..688e277f0335 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -928,6 +928,13 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx int i, ret, off, nr; unsigned int nbufs;

+ /* + * Accounting state is shared between the two rings; that only works if + * both rings are accounted towards the same counters. + */ + if (ctx->user != src_ctx->user || ctx->mm_account != src_ctx->mm_account) + return -EINVAL; + /* if offsets are given, must have nr specified too */ if (!arg->nr && (arg->dst_off || arg->src_off)) return -EINVAL;