From: Dongsheng Yang <dongsheng.yang@easystack.cn>
To: colyli@suse.de
Cc: linux-bcache@vger.kernel.org,
Dongsheng Yang <dongsheng.yang@easystack.cn>
Subject: [PATCH] bcache: check c->root with IS_ERR_OR_NULL() in mca_reserve()
Date: Thu, 17 Sep 2020 08:13:26 +0000 [thread overview]
Message-ID: <1600330406-2484-1-git-send-email-dongsheng.yang@easystack.cn> (raw)
In mca_reserve(c) macro, we are checking root whether is NULL or not.
But that's not enough, when we read the root node in run_cache_set(),
if we got an error in bch_btree_node_read_done(), we will return ERR_PTR(-EIO)
to c->root.
And then we will go continue to unregister, but before unregister_shrinker(&c->shrink);
there is a possibility to call bch_mca_count(), and we would get a crash with call trace like that:
[ 2149.876008] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b5
... ...
[ 2150.598931] Call trace:
[ 2150.606439] bch_mca_count+0x58/0x98 [escache]
[ 2150.615866] do_shrink_slab+0x54/0x310
[ 2150.624429] shrink_slab+0x248/0x2d0
[ 2150.632633] drop_slab_node+0x54/0x88
[ 2150.640746] drop_slab+0x50/0x88
[ 2150.648228] drop_caches_sysctl_handler+0xf0/0x118
[ 2150.657219] proc_sys_call_handler.isra.18+0xb8/0x110
[ 2150.666342] proc_sys_write+0x40/0x50
[ 2150.673889] __vfs_write+0x48/0x90
[ 2150.681095] vfs_write+0xac/0x1b8
[ 2150.688145] ksys_write+0x6c/0xd0
[ 2150.695127] __arm64_sys_write+0x24/0x30
[ 2150.702749] el0_svc_handler+0xa0/0x128
[ 2150.710296] el0_svc+0x8/0xc
Signed-off-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
---
drivers/md/bcache/btree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index d45a1dd..36cae5c 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -514,7 +514,7 @@ static void bch_btree_leaf_dirty(struct btree *b, atomic_t *journal_ref)
* mca -> memory cache
*/
-#define mca_reserve(c) (((c->root && c->root->level) \
+#define mca_reserve(c) (((!IS_ERR_OR_NULL(c->root) && c->root->level) \
? c->root->level : 1) * 8 + 16)
#define mca_can_free(c) \
max_t(int, 0, c->btree_cache_used - mca_reserve(c))
--
1.8.3.1
next reply other threads:[~2020-09-17 8:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 8:13 Dongsheng Yang [this message]
2020-09-18 10:14 ` [PATCH] bcache: check c->root with IS_ERR_OR_NULL() in mca_reserve() Coly Li
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