All of lore.kernel.org
 help / color / mirror / Atom feed
From: Dennis Zhou <dennis@kernel.org>
To: Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Dennis Zhou <dennis@kernel.org>, Tom Rix <trix@redhat.com>
Subject: [PATCH 1/1] percpu: initialize best_upa variable
Date: Mon, 14 Jun 2021 14:50:49 +0000	[thread overview]
Message-ID: <20210614145049.1585477-1-dennis@kernel.org> (raw)

Tom reported this finding from clang 10's static analysis [1].

Due to the way the code is written, it will always see a successful loop
iteration. Instead of setting an initial value, check that it was set
instead with BUG_ON() because 0 units per allocation is bogus.

[1] https://lore.kernel.org/lkml/20210515180817.1751084-1-trix@redhat.com/

Reported-by: Tom Rix <trix@redhat.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
Sorry this hasn't been my highest priority. I'll apply this shortly to
for-5.14.

 mm/percpu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/percpu.c b/mm/percpu.c
index e7b9ca82e9aa..6667dfa0fcec 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -2888,6 +2888,7 @@ static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info(
 	 * Related to atom_size, which could be much larger than the unit_size.
 	 */
 	last_allocs = INT_MAX;
+	best_upa = 0;
 	for (upa = max_upa; upa; upa--) {
 		int allocs = 0, wasted = 0;
 
@@ -2914,6 +2915,7 @@ static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info(
 		last_allocs = allocs;
 		best_upa = upa;
 	}
+	BUG_ON(!best_upa);
 	upa = best_upa;
 
 	/* allocate and fill alloc_info */
-- 
2.32.0.272.g935e593368-goog


                 reply	other threads:[~2021-06-14 14:51 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210614145049.1585477-1-dennis@kernel.org \
    --to=dennis@kernel.org \
    --cc=cl@linux.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=tj@kernel.org \
    --cc=trix@redhat.com \
    --subject='Re: [PATCH 1/1] percpu: initialize best_upa variable' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.