bcache: check c->root with IS_ERR_OR_NULL() in mca_reserve()
PATCH 1/1 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 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
--- drivers/md/bcache/btree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/md/bcache/btree.c +1 -1
@@ -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))
Signature · 1 line
1.8.3.1
Quoted 26 lines · Dongsheng Yang
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 inrun_cache_set(), if we got an error inbch_btree_node_read_done(), we will returnERR_PTR(-EIO)toc->root.And then we will go continue to unregister, but before
unregister_shrinker(&c->shrink); there is a possibility to callbch_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
Quoted 1 line
Signed-off-by Dongsheng Yang <[email protected]>
It looks good to me, added into my test queue.
Thanks.
Coly Li
Quoted 18 lines
--- drivers/md/bcache/btree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)drivers/md/bcache/btree.c +1
-1@@ -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))