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authorDongsheng Yang <dongsheng.yang@easystack.cn>2020-10-01 14:50:43 +0800
committerJens Axboe <axboe@kernel.dk>2020-10-02 14:25:29 -0600
commit7e59c506c338d1e42ed19f24f1a737aff8b18fc3 (patch)
treeaf5729bacc3bfe4e36f29700d153d121b92700cf /drivers/md
parenta58e88bfdc4d527f99827b8d66ecf68d05c3ac87 (diff)
bcache: check c->root with IS_ERR_OR_NULL() in mca_reserve()
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 calling 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> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/bcache/btree.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 3d8bd0692af3..ae7611fa42bf 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))