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io_uring: used cached copies of sq->dropped and cq->overflow 

We currently use the ring values directly, but that can lead to issues
if the application is malicious and changes these values on our behalf.
Created in-kernel cached versions of them, and just overwrite the user
side when we update them. This is similar to how we treat the sq/cq
ring tail/head updates.

Reported-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2019-10-25 10:04:25 -06:00
parent 935d1e4590
commit 498ccd9eda
1 changed files with 8 additions and 5 deletions
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13
fs/io_uring.c
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@ -197,6 +197,7 @@ struct io_ring_ctx {
unsigned sq_entries;
unsigned sq_mask;
unsigned sq_thread_idle;
unsigned cached_sq_dropped;
struct io_uring_sqe *sq_sqes;
struct list_head defer_list;
@ -212,6 +213,7 @@ struct io_ring_ctx {
struct {
unsigned cached_cq_tail;
atomic_t cached_cq_overflow;
unsigned cq_entries;
unsigned cq_mask;
struct wait_queue_head cq_wait;
@ -420,7 +422,8 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
static inline bool __io_sequence_defer(struct io_ring_ctx *ctx,
struct io_kiocb *req)
{
return req->sequence != ctx->cached_cq_tail + ctx->rings->sq_dropped;
return req->sequence != ctx->cached_cq_tail + ctx->cached_sq_dropped
+ atomic_read(&ctx->cached_cq_overflow);
}
static inline bool io_sequence_defer(struct io_ring_ctx *ctx,
@ -567,9 +570,8 @@ static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data,
WRITE_ONCE(cqe->res, res);
WRITE_ONCE(cqe->flags, 0);
} else {
unsigned overflow = READ_ONCE(ctx->rings->cq_overflow);
WRITE_ONCE(ctx->rings->cq_overflow, overflow + 1);
WRITE_ONCE(ctx->rings->cq_overflow,
atomic_inc_return(&ctx->cached_cq_overflow));
}
}
@ -2564,7 +2566,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
/* drop invalid entries */
ctx->cached_sq_head++;
rings->sq_dropped++;
ctx->cached_sq_dropped++;
WRITE_ONCE(rings->sq_dropped, ctx->cached_sq_dropped);
return false;
}