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io_uring/bpf-ops: restrict ctx access to BPF

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BPF programs should have no need in looking into struct io_ring_ctx, if
anything, most of such cases would be anti patterns like looking up ring
indices directly via the context.

Replace it with a new empty structure, which is just an alias to struct
io_ring_ctx. It'll create a new BTF type and fail verification if a BPF
program tries to access it (beyond the first byte). It'll also give more
flexibility for the future, and otherwise it can be made aligned with
io_ring_ctx as before with struct groups if ever needed or extended in a
different way.

Fixes: d0e437b76b ("io_uring/bpf-ops: implement loop_step with BPF struct_ops")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/5f6ca3649e9e0bae8667db4357e28dd00cd07901.1780394491.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2026-06-02 11:08:25 +01:00 committed by Jens Axboe
parent 29bef9934b
commit ec02fe217f
5 changed files with 21 additions and 6 deletions
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4
include/linux/io_uring_types.h
View File

@ -290,6 +290,8 @@ enum {
IO_RING_F_IOWQ_LIMITS_SET = BIT(12), IO_RING_F_IOWQ_LIMITS_SET = BIT(12),
}; };
struct iou_ctx {};
struct io_ring_ctx { struct io_ring_ctx {
/* const or read-mostly hot data */ /* const or read-mostly hot data */
struct { struct {
@ -366,7 +368,7 @@ struct io_ring_ctx {
struct io_alloc_cache rw_cache; struct io_alloc_cache rw_cache;
struct io_alloc_cache cmd_cache; struct io_alloc_cache cmd_cache;
int (*loop_step)(struct io_ring_ctx *ctx, int (*loop_step)(struct iou_ctx *,
struct iou_loop_params *); struct iou_loop_params *);
/* /*

9
io_uring/bpf-ops.c
View File

@ -14,15 +14,18 @@ static const struct btf_type *loop_params_type;
__bpf_kfunc_start_defs(); __bpf_kfunc_start_defs();
__bpf_kfunc int bpf_io_uring_submit_sqes(struct io_ring_ctx *ctx, u32 nr) __bpf_kfunc int bpf_io_uring_submit_sqes(struct iou_ctx *loop_ctx, u32 nr)
{ {
struct io_ring_ctx *ctx = io_loop_demangle_ctx(loop_ctx);
return io_submit_sqes(ctx, nr); return io_submit_sqes(ctx, nr);
} }
__bpf_kfunc __bpf_kfunc
__u8 *bpf_io_uring_get_region(struct io_ring_ctx *ctx, __u32 region_id, __u8 *bpf_io_uring_get_region(struct iou_ctx *loop_ctx, __u32 region_id,
const size_t rdwr_buf_size) const size_t rdwr_buf_size)
{ {
struct io_ring_ctx *ctx = io_loop_demangle_ctx(loop_ctx);
struct io_mapped_region *r; struct io_mapped_region *r;
lockdep_assert_held(&ctx->uring_lock); lockdep_assert_held(&ctx->uring_lock);
@ -58,7 +61,7 @@ static const struct btf_kfunc_id_set bpf_io_uring_kfunc_set = {
.set = &io_uring_kfunc_set, .set = &io_uring_kfunc_set,
}; };
static int io_bpf_ops__loop_step(struct io_ring_ctx *ctx, static int io_bpf_ops__loop_step(struct iou_ctx *ctx,
struct iou_loop_params *lp) struct iou_loop_params *lp)
{ {
return IOU_LOOP_STOP; return IOU_LOOP_STOP;

2
io_uring/bpf-ops.h
View File

@ -11,7 +11,7 @@ enum {
}; };
struct io_uring_bpf_ops { struct io_uring_bpf_ops {
int (*loop_step)(struct io_ring_ctx *ctx, struct iou_loop_params *lp); int (*loop_step)(struct iou_ctx *, struct iou_loop_params *lp);
__u32 ring_fd; __u32 ring_fd;
void *priv; void *priv;

2
io_uring/loop.c
View File

@ -49,7 +49,7 @@ static int __io_run_loop(struct io_ring_ctx *ctx)
if (unlikely(!ctx->loop_step)) if (unlikely(!ctx->loop_step))
return -EFAULT; return -EFAULT;
step_res = ctx->loop_step(ctx, &lp); step_res = ctx->loop_step(io_loop_mangle_ctx(ctx), &lp);
if (step_res == IOU_LOOP_STOP) if (step_res == IOU_LOOP_STOP)
break; break;
if (step_res != IOU_LOOP_CONTINUE) if (step_res != IOU_LOOP_CONTINUE)

10
io_uring/loop.h
View File

@ -24,4 +24,14 @@ static inline bool io_has_loop_ops(struct io_ring_ctx *ctx)
int io_run_loop(struct io_ring_ctx *ctx); int io_run_loop(struct io_ring_ctx *ctx);
static inline struct iou_ctx *io_loop_mangle_ctx(struct io_ring_ctx *ctx)
{
return (struct iou_ctx *)ctx;
}
static inline struct io_ring_ctx *io_loop_demangle_ctx(struct iou_ctx *ctx)
{
return (struct io_ring_ctx *)ctx;
}
#endif #endif