在 2019/6/13 下午7:10, Dominique Martinet 写道: > Lu Shuaibing wrote on Thu, Jun 13, 2019: >> The p9_tag_alloc() does not initialize the transport error t_err field. >> The struct p9_req_t *req is allocated and stored in a struct p9_client >> variable. The field t_err is never initialized before p9_conn_cancel() >> checks its value. >> >> KUMSAN(KernelUninitializedMemorySantizer, a new error detection tool) >> reports this bug. >> >> ================================================================== >> BUG: KUMSAN: use of uninitialized memory in p9_conn_cancel+0x2d9/0x3b0 >> Read of size 4 at addr ffff88805f9b600c by task kworker/1:2/1216 >> >> CPU: 1 PID: 1216 Comm: kworker/1:2 Not tainted 5.2.0-rc4+ #28 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS >> Ubuntu-1.8.2-1ubuntu1 04/01/2014 >> Workqueue: events p9_write_work >> Call Trace: >> dump_stack+0x75/0xae >> __kumsan_report+0x17c/0x3e6 >> kumsan_report+0xe/0x20 >> p9_conn_cancel+0x2d9/0x3b0 >> p9_write_work+0x183/0x4a0 >> process_one_work+0x4d1/0x8c0 >> worker_thread+0x6e/0x780 >> kthread+0x1ca/0x1f0 >> ret_from_fork+0x35/0x40 >> >> Allocated by task 1979: >> save_stack+0x19/0x80 >> __kumsan_kmalloc.constprop.3+0xbc/0x120 >> kmem_cache_alloc+0xa7/0x170 >> p9_client_prepare_req.part.9+0x3b/0x380 >> p9_client_rpc+0x15e/0x880 >> p9_client_create+0x3d0/0xac0 >> v9fs_session_init+0x192/0xc80 >> v9fs_mount+0x67/0x470 >> legacy_get_tree+0x70/0xd0 >> vfs_get_tree+0x4a/0x1c0 >> do_mount+0xba9/0xf90 >> ksys_mount+0xa8/0x120 >> __x64_sys_mount+0x62/0x70 >> do_syscall_64+0x6d/0x1e0 >> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> >> Freed by task 0: >> (stack is not available) >> >> The buggy address belongs to the object at ffff88805f9b6008 >> which belongs to the cache p9_req_t of size 144 >> The buggy address is located 4 bytes inside of >> 144-byte region [ffff88805f9b6008, ffff88805f9b6098) >> The buggy address belongs to the page: >> page:ffffea00017e6d80 refcount:1 mapcount:0 mapping:ffff888068b63740 >> index:0xffff88805f9b7d90 compound_mapcount: 0 >> flags: 0x100000000010200(slab|head) >> raw: 0100000000010200 ffff888068b66450 ffff888068b66450 ffff888068b63740 >> raw: ffff88805f9b7d90 0000000000100001 00000001ffffffff 0000000000000000 >> page dumped because: kumsan: bad access detected >> ================================================================== >> >> Signed-off-by: Lu Shuaibing <shuaibin...@126.com> > Looks good to me, will queue it up for -next after I've had time to run > some tests - probably early next week. > > This made me realize that this refcount_set is too late, it is possible > in theory to find the request with p9_tag_lookup as soon as the tag > alloc worked so both this req->t_err and refcount initialization should > go before the idr chunk with the other field initializations. > > I also checked by the way that no other fields were forgotten, the only > field that is not initialized now is ->aux, but that field is never used > so it might be just as fast to remove the field instead... > I'll submit a couple of patches to move these two inits up and remove > the aux field when I find time. > > > Thanks!
Thanks for your reply. The kumsan tool finds only one field is used initialized. The ->aux field could be replaced.
