linux-kernel - [PATCH 5.4 68/76] mm, slub: consider rest of partial list if acquire

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210118113344.220384656@linuxfoundation.org>
Date:   Mon, 18 Jan 2021 12:35:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jann Horn <jannh@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.4 68/76] mm, slub: consider rest of partial list if acquire_slab() fails

From: Jann Horn <jannh@...gle.com>

commit 8ff60eb052eeba95cfb3efe16b08c9199f8121cf upstream.

acquire_slab() fails if there is contention on the freelist of the page
(probably because some other CPU is concurrently freeing an object from
the page).  In that case, it might make sense to look for a different page
(since there might be more remote frees to the page from other CPUs, and
we don't want contention on struct page).

However, the current code accidentally stops looking at the partial list
completely in that case.  Especially on kernels without CONFIG_NUMA set,
this means that get_partial() fails and new_slab_objects() falls back to
new_slab(), allocating new pages.  This could lead to an unnecessary
increase in memory fragmentation.

Link: https://lkml.kernel.org/r/20201228130853.1871516-1-jannh@google.com
Fixes: 7ced37197196 ("slub: Acquire_slab() avoid loop")
Signed-off-by: Jann Horn <jannh@...gle.com>
Acked-by: David Rientjes <rientjes@...gle.com>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/slub.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1887,7 +1887,7 @@ static void *get_partial_node(struct kme
 
 		t = acquire_slab(s, n, page, object == NULL, &objects);
 		if (!t)
-			break;
+			continue; /* cmpxchg raced */
 
 		available += objects;
 		if (!object) {