6.13-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit 19d340a2988d4f3e673cded9dde405d727d7e248 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/rsrc.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -931,6 +931,13 @@ static int io_clone_buffers(struct io_ri 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;