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io_uring/rsrc: require cloned buffers to share accounting contexts

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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_TMcbvRA01bg@mail.gmail.com
Fixes: 7cc2a6eadc ("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@google.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jann Horn 2025-01-14 18:49:00 +01:00 committed by Jens Axboe
parent a13030fd19
commit 19d340a298
1 changed files with 7 additions and 0 deletions
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7
io_uring/rsrc.c
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@ -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;