On 03/21/2019 11:00 AM, Xu Yu wrote: > Syzkaller hit 'KASAN: use-after-free Write in sanitize_ptr_alu' bug. > Call trace: > dump_stack+0xbf/0x12e > print_address_description+0x6a/0x280 > kasan_report+0x237/0x360 > sanitize_ptr_alu+0x85a/0x8d0 > adjust_ptr_min_max_vals+0x8f2/0x1ca0 > adjust_reg_min_max_vals+0x8ed/0x22e0 > do_check+0x1ca6/0x5d00 > bpf_check+0x9ca/0x2570 > bpf_prog_load+0xc91/0x1030 > __se_sys_bpf+0x61e/0x1f00 > do_syscall_64+0xc8/0x550 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > Fault injection trace: > kfree+0xea/0x290 > free_func_state+0x4a/0x60 > free_verifier_state+0x61/0xe0 > push_stack+0x216/0x2f0 <- inject failslab > sanitize_ptr_alu+0x2b1/0x8d0 > adjust_ptr_min_max_vals+0x8f2/0x1ca0 > adjust_reg_min_max_vals+0x8ed/0x22e0 > do_check+0x1ca6/0x5d00 > bpf_check+0x9ca/0x2570 > bpf_prog_load+0xc91/0x1030 > __se_sys_bpf+0x61e/0x1f00 > do_syscall_64+0xc8/0x550 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > When kzalloc() fails in push_stack(), free_verifier_state() will free > current verifier state. As push_stack() returns, dst_reg was restored > if ptr_is_dst_reg is false. However, as member of the cur_state, dst_reg > is also freed, and error occurs when dereferencing dst_reg. > > Simply fix it by testing ret of push_stack() before retoring dst_reg. > > Signed-off-by: Xu Yu <xuyu@xxxxxxxxxxxxxxxxx> Applied, thanks!
