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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Mar 2025 04:02:23.1400 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: bbeed5cf-8db7-4d4a-461d-08dd6dad5830 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ5PEPF00000208.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5897 Hello Dominique, On 3/28/2025 3:48 AM, asmadeus@codewreck.org wrote: > syzbot wrote on Thu, Mar 27, 2025 at 02:19:03PM -0700: >> BUG: KASAN: slab-use-after-free in p9_conn_cancel+0x900/0x910 net/9p/trans_fd.c:205 >> Read of size 8 at addr ffff88807b19ea50 by task syz-executor/6595 Woops! Should have tested with KASAN enabled. This time I did. > > Ugh, why... > Ah, if ->request() fails p9_client_rpc assumes the request was not > written (e.g. write error), so you can't return an error after the > list_add_tail call in p9_fd_request. > > I think you can call p9_conn_cancel with the error and return 0 anyway, > and this paticular workaround will probably work, regardless of whether > it's the correct thing to do here (still haven't had time to look at the > patch here) That works too! Thank you for the pointer. > > Sorry for this mess (even if most of it predates me...) And I'm sorry for the noise from hacking on stuff that I don't fully understand. Fingers crossed (and thank you syzbot) #syz test: upstream aaec5a95d59615523db03dd53c2052f0a87beea7 diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index 196060dc6138..dab7f02dc243 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -687,7 +687,13 @@ static int p9_fd_request(struct p9_client *client, struct p9_req_t *req) else n = p9_fd_poll(m->client, NULL, NULL); - if (n & EPOLLOUT && !test_and_set_bit(Wworksched, &m->wsched)) + /* Failed to send request */ + if (!(n & EPOLLOUT)) { + p9_conn_cancel(m, -EIO); + return 0; + } + + if (!test_and_set_bit(Wworksched, &m->wsched)) schedule_work(&m->wq); return 0;