Messages in this thread | | | Date | Thu, 13 Jun 2019 13:10:27 +0200 | From | Dominique Martinet <> | Subject | Re: [PATCH] 9p: Transport error uninitialized |
| |
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 <shuaibinglu@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! -- Dominique
| |