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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 ================================================================== Link: http://lkml.kernel.org/r/20190613070854.10434-1-shuaibinglu@126.com Signed-off-by: Lu Shuaibing <shuaibinglu@126.com> [dominique.martinet@cea.fr: grouped the added init with the others] Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.