Re: [PATCH v2 2/2] io_uring: Improve exception handling in io_ring_ctx_alloc()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 1/10/24 20:50, Markus Elfring wrote:
From: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 10 Jan 2024 21:15:48 +0100

The label “err” was used to jump to a kfree() call despite of
the detail in the implementation of the function “io_ring_ctx_alloc”
that it was determined already that a corresponding variable contained
a null pointer because of a failed memory allocation.

It's _much_ simpler the way it currently is, compare it with maintaining
a bunch of labels. That is the advantage of being able to distinguish
un-allocated state like NULL, just kfree them and don't care about
jumping to a wrong one or keeping them in order.

1. Thus use more appropriate labels instead.

2. Reorder jump targets at the end.

Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
---

See also:
https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consider+using+a+goto+chain+when+leaving+a+function+on+error+when+using+and+releasing+resources


  io_uring/io_uring.c | 15 ++++++++++-----
  1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index c9a63c39cdd0..7727cdd505ae 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -295,12 +295,14 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
  	hash_bits = ilog2(p->cq_entries) - 5;
  	hash_bits = clamp(hash_bits, 1, 8);
  	if (io_alloc_hash_table(&ctx->cancel_table, hash_bits))
-		goto err;
+		goto destroy_io_bl_xa;
+
  	if (io_alloc_hash_table(&ctx->cancel_table_locked, hash_bits))
-		goto err;
+		goto free_cancel_table_hbs;
+
  	if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
  			    0, GFP_KERNEL))
-		goto err;
+		goto free_cancel_table_locked_hbs;

  	ctx->flags = p->flags;
  	init_waitqueue_head(&ctx->sqo_sq_wait);
@@ -341,9 +343,12 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
  	INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
  	INIT_HLIST_HEAD(&ctx->cancelable_uring_cmd);
  	return ctx;
-err:
-	kfree(ctx->cancel_table.hbs);
+
+free_cancel_table_locked_hbs:
  	kfree(ctx->cancel_table_locked.hbs);
+free_cancel_table_hbs:
+	kfree(ctx->cancel_table.hbs);
+destroy_io_bl_xa:
  	xa_destroy(&ctx->io_bl_xa);
  	kfree(ctx);
  	return NULL;
--
2.43.0


--
Pavel Begunkov




[Index of Archives]     [Kernel Development]     [Kernel Announce]     [Kernel Newbies]     [Linux Networking Development]     [Share Photos]     [IDE]     [Security]     [Git]     [Netfilter]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Device Mapper]

  Powered by Linux