From: Jiri Pirko jiri@mellanox.com
[ Upstream commit df45bf84e4f5a48f23d4b1a07d21d5 ]
Since the block is freed with last chain being put, once we reach the end of iteration of list_for_each_entry_safe, the block may be already freed. I'm hitting this only by creating and deleting clsact:
[ 202.171952] ================================================================== [ 202.180182] BUG: KASAN: use-after-free in tcf_block_put_ext+0x240/0x390 [ 202.187590] Read of size 8 at addr ffff880225539a80 by task tc/796 [ 202.194508] [ 202.196185] CPU: 0 PID: 796 Comm: tc Not tainted 4.15.0-rc2jiri+ #5 [ 202.203200] Hardware name: Mellanox Technologies Ltd. "MSN2100-CB2F"/"SA001017", BIOS 5.6.5 06/07/2016 [ 202.213613] Call Trace: [ 202.216369] dump_stack+0xda/0x169 [ 202.220192] ? dma_virt_map_sg+0x147/0x147 [ 202.224790] ? show_regs_print_info+0x54/0x54 [ 202.229691] ? tcf_chain_destroy+0x1dc/0x250 [ 202.234494] print_address_description+0x83/0x3d0 [ 202.239781] ? tcf_block_put_ext+0x240/0x390 [ 202.244575] kasan_report+0x1ba/0x460 [ 202.248707] ? tcf_block_put_ext+0x240/0x390 [ 202.253518] tcf_block_put_ext+0x240/0x390 [ 202.258117] ? tcf_chain_flush+0x290/0x290 [ 202.262708] ? qdisc_hash_del+0x82/0x1a0 [ 202.267111] ? qdisc_hash_add+0x50/0x50 [ 202.271411] ? __lock_is_held+0x5f/0x1a0 [ 202.275843] clsact_destroy+0x3d/0x80 [sch_ingress] [ 202.281323] qdisc_destroy+0xcb/0x240 [ 202.285445] qdisc_graft+0x216/0x7b0 [ 202.289497] tc_get_qdisc+0x260/0x560
Fix this by holding the block also by chain 0 and put chain 0 explicitly, out of the list_for_each_entry_safe loop at the very end of tcf_block_put_ext.
Fixes: efbf78973978 ("net_sched: get rid of rcu_barrier() in tcf_block_put_ext()") Signed-off-by: Jiri Pirko jiri@mellanox.com Signed-off-by: David S. Miller davem@davemloft.net --- net/sched/cls_api.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index 135147c1deed..934c239cf98d 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -290,21 +290,22 @@ void tcf_block_put(struct tcf_block *block) if (!block) return;
- /* Hold a refcnt for all chains, except 0, so that they don't disappear + /* Hold a refcnt for all chains, so that they don't disappear * while we are iterating. */ list_for_each_entry(chain, &block->chain_list, list) - if (chain->index) - tcf_chain_hold(chain); + tcf_chain_hold(chain);
list_for_each_entry(chain, &block->chain_list, list) tcf_chain_flush(chain);
- /* At this point, all the chains should have refcnt >= 1. Block will be - * freed after all chains are gone. - */ + /* At this point, all the chains should have refcnt >= 1. */ list_for_each_entry_safe(chain, tmp, &block->chain_list, list) tcf_chain_put(chain); + + /* Finally, put chain 0 and allow block to be freed. */ + chain = list_first_entry(&block->chain_list, struct tcf_chain, list); + tcf_chain_put(chain); } EXPORT_SYMBOL(tcf_block_put);