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io_uring/register: don't exempt disabled rings from task restrictions

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A ring created with IORING_SETUP_R_DISABLED is exempt from its register
restrictions until it is enabled. This lets the creator register the
restrictions and then enable the ring with IORING_REGISTER_ENABLE_RINGS,
whether or not that opcode is in the allowed set.

Since commit ed82f35b92 ("io_uring: allow registration of per-task
restrictions"), a ring also inherits restrictions from the task that
creates it, and the same exemption applies to those. A task whose
register opcodes are restricted can therefore create a disabled ring,
issue any register opcode on it, and then enable it.

Mark rings whose restrictions were inherited from the task, and keep
checking register opcodes for them while the ring is disabled. Enabling
such a ring now requires IORING_REGISTER_ENABLE_RINGS to be in the
task's allowed set. Per-ring restrictions registered on a disabled ring
work as before.

Fixes: ed82f35b92 ("io_uring: allow registration of per-task restrictions")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Eugene Gvozdetsky <gvozdet@gmail.com>
Link: https://patch.msgid.link/20261009-iouring-task-restrict-fix-v1-1-a49daf55a12c@gmail.com
[axboe: amend with inheritance flag fixup]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Eugene Gvozdetsky 2026-10-09 01:08:49 +02:00 committed by Jens Axboe
parent cde56daf4b
commit 6da8f402e3
3 changed files with 12 additions and 2 deletions
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2
include/linux/io_uring_types.h
View File

@ -317,6 +317,8 @@ enum {
IO_RING_F_DRAIN_DISABLED = BIT(10),
IO_RING_F_COMPAT = BIT(11),
IO_RING_F_IOWQ_LIMITS_SET = BIT(12),
/* restrictions were inherited from the task that created the ring */
IO_RING_F_RESTRICT_INHERITED = BIT(13),
};
struct iou_ctx {};

3
io_uring/io_uring.c
View File

@ -2962,7 +2962,8 @@ static void io_ctx_restriction_clone(struct io_ring_ctx *ctx,
if (dst->op_registered)
ctx->int_flags |= IO_RING_F_OP_RESTRICTED;
if (dst->reg_registered)
ctx->int_flags |= IO_RING_F_REG_RESTRICTED;
ctx->int_flags |= IO_RING_F_REG_RESTRICTED |
IO_RING_F_RESTRICT_INHERITED;
}
static __cold int io_uring_create(struct io_ctx_config *config)

9
io_uring/register.c
View File

@ -766,7 +766,14 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (ctx->submitter_task && ctx->submitter_task != current)
return -EEXIST;
if ((ctx->int_flags & IO_RING_F_REG_RESTRICTED) && !(ctx->flags & IORING_SETUP_R_DISABLED)) {
/*
* A disabled ring is exempt from its own register restrictions, so
* that the creator can set them up and then enable the ring. That
* does not apply to restrictions inherited from the task.
*/
if ((ctx->int_flags & IO_RING_F_REG_RESTRICTED) &&
(!(ctx->flags & IORING_SETUP_R_DISABLED) ||
(ctx->int_flags & IO_RING_F_RESTRICT_INHERITED))) {
opcode = array_index_nospec(opcode, IORING_REGISTER_LAST);
if (!test_bit(opcode, ctx->restrictions.register_op))
return -EACCES;