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io_uring/kbuf: protect io_buffer_list teardown with a reference

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commit 6b69c4ab4f685327d9e10caf0d84217ba23a8c4b upstream.

No functional changes in this patch, just in preparation for being able
to keep the buffer list alive outside of the ctx->uring_lock.

Cc: stable@vger.kernel.org # v6.4+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jens Axboe 2024-03-15 16:12:51 -06:00 committed by Greg Kroah-Hartman
parent 4c0a5da0e7
commit b392402d29
2 changed files with 13 additions and 4 deletions
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15
io_uring/kbuf.c
View File

@ -59,6 +59,7 @@ static int io_buffer_add_list(struct io_ring_ctx *ctx,
* always under the ->uring_lock, but the RCU lookup from mmap does.
*/
bl->bgid = bgid;
atomic_set(&bl->refs, 1);
return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
}
@ -272,6 +273,14 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx,
return i;
}
static void io_put_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
{
if (atomic_dec_and_test(&bl->refs)) {
__io_remove_buffers(ctx, bl, -1U);
kfree_rcu(bl, rcu);
}
}
void io_destroy_buffers(struct io_ring_ctx *ctx)
{
struct io_buffer_list *bl;
@ -279,8 +288,7 @@ void io_destroy_buffers(struct io_ring_ctx *ctx)
xa_for_each(&ctx->io_bl_xa, index, bl) {
xa_erase(&ctx->io_bl_xa, bl->bgid);
__io_remove_buffers(ctx, bl, -1U);
kfree_rcu(bl, rcu);
io_put_bl(ctx, bl);
}
while (!list_empty(&ctx->io_buffers_pages)) {
@ -676,9 +684,8 @@ int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
if (!bl->is_mapped)
return -EINVAL;
__io_remove_buffers(ctx, bl, -1U);
xa_erase(&ctx->io_bl_xa, bl->bgid);
kfree_rcu(bl, rcu);
io_put_bl(ctx, bl);
return 0;
}

2
io_uring/kbuf.h
View File

@ -25,6 +25,8 @@ struct io_buffer_list {
__u16 head;
__u16 mask;
atomic_t refs;
/* ring mapped provided buffers */
__u8 is_mapped;
/* ring mapped provided buffers, but mmap'ed by application */