linux-kernel - [PATCH 4.19 37/66] slab: fix a crash by reading /proc/slab

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Date:   Thu,  9 May 2019 20:42:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Qian Cai <cai@....pw>,
        "Tobin C. Harding" <tobin@...nel.org>, Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 37/66] slab: fix a crash by reading /proc/slab_allocators

[ Upstream commit fcf88917dd435c6a4cb2830cb086ee58605a1d85 ]

The commit 510ded33e075 ("slab: implement slab_root_caches list")
changes the name of the list node within "struct kmem_cache" from "list"
to "root_caches_node", but leaks_show() still use the "list" which
causes a crash when reading /proc/slab_allocators.

You need to have CONFIG_SLAB=y and CONFIG_MEMCG=y to see the problem,
because without MEMCG all slab caches are root caches, and the "list"
node happens to be the right one.

Fixes: 510ded33e075 ("slab: implement slab_root_caches list")
Signed-off-by: Qian Cai <cai@....pw>
Reviewed-by: Tobin C. Harding <tobin@...nel.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/slab.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/slab.c b/mm/slab.c
index b8e0ec74330f3..018d32496e8d1 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4305,7 +4305,8 @@ static void show_symbol(struct seq_file *m, unsigned long address)
 
 static int leaks_show(struct seq_file *m, void *p)
 {
-	struct kmem_cache *cachep = list_entry(p, struct kmem_cache, list);
+	struct kmem_cache *cachep = list_entry(p, struct kmem_cache,
+					       root_caches_node);
 	struct page *page;
 	struct kmem_cache_node *n;
 	const char *name;
-- 
2.20.1