On 1/11/25 7:07 AM, lizetao wrote: > Hi all, > > When I run the testcase liburing/accept-reust.t with CONFIG_KASAN=y and CONFIG_KASAN_EXTRA_INFO=y, I got > a error reported by KASAN: Looks more like you get KASAN crashing... > Unable to handle kernel paging request at virtual address 00000c6455008008 > Mem abort info: > ESR = 0x0000000096000004 > EC = 0x25: DABT (current EL), IL = 32 bits > SET = 0, FnV = 0 > EA = 0, S1PTW = 0 > FSC = 0x04: level 0 translation fault > Data abort info: > ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 > CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > user pgtable: 4k pages, 48-bit VAs, pgdp=00000001104c5000 > [00000c6455008008] pgd=0000000000000000, p4d=0000000000000000 > Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP > Modules linked in: > CPU: 6 UID: 0 PID: 352 Comm: kworker/u128:5 Not tainted 6.13.0-rc6-g0a2cb793507d #5 > Hardware name: linux,dummy-virt (DT) > Workqueue: iou_exit io_ring_exit_work > pstate: 10000005 (nzcV daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : __kasan_mempool_unpoison_object+0x38/0x170 > lr : io_netmsg_cache_free+0x8c/0x180 > sp : ffff800083297a90 > x29: ffff800083297a90 x28: ffffd4d7f67e88e4 x27: 0000000000000003 > x26: 1fffe5958011502e x25: ffff2cabff976c18 x24: 1fffe5957ff2ed83 > x23: ffff2cabff976c10 x22: 00000c6455008000 x21: 0002992540200001 > x20: 0000000000000000 x19: 00000c6455008000 x18: 00000000489683f8 > x17: ffffd4d7f68006ac x16: ffffd4d7f67eb3e0 x15: ffffd4d7f67e88e4 > x14: ffffd4d7f766deac x13: ffffd4d7f6619030 x12: ffff7a9b012e3e26 > x11: 1ffffa9b012e3e25 x10: ffff7a9b012e3e25 x9 : ffffd4d7f766debc > x8 : ffffd4d80971f128 x7 : 0000000000000001 x6 : 00008564fed1c1db > x5 : ffffd4d80971f128 x4 : ffff7a9b012e3e26 x3 : ffff2cabff976c00 > x2 : ffffc1ffc0000000 x1 : 0000000000000000 x0 : 0002992540200001 > Call trace: > __kasan_mempool_unpoison_object+0x38/0x170 (P) > io_netmsg_cache_free+0x8c/0x180 > io_ring_exit_work+0xd4c/0x13a0 > process_one_work+0x52c/0x1000 > worker_thread+0x830/0xdc0 > kthread+0x2bc/0x348 > ret_from_fork+0x10/0x20 > Code: aa0003f5 aa0103f4 8b131853 aa1303f6 (f9400662) > ---[ end trace 0000000000000000 ]--- > > > I preliminary analyzed the accept and connect code logic. In the > accept-reuse.t testcase, kmsg->free_iov is not used, so when calling > io_netmsg_cache_free(), the > kasan_mempool_unpoison_object(kmsg->free_iov...) path should not be > executed. > > > I used the hardware watchpoint to capture the first scene of modifying kmsg->free_iov: > > Thread 3 hit Hardware watchpoint 7: *0xffff0000ebfc5410 > Old value = 0 > New value = -211812350 > kasan_set_track (stack=<optimized out>, track=<optimized out>) at ./arch/arm64/include/asm/current.h:21 > 21 return (struct task_struct *)sp_el0; > > # bt > kasan_set_track > kasan_save_track > kasan_save_free_info > poison_slab_object > __kasan_mempool_poison_object > kasan_mempool_poison_object > io_alloc_cache_put > io_netmsg_recycle > io_req_msg_cleanup > io_connect > io_issue_sqe > io_queue_sqe > io_req_task_submit > ... > > > It's a bit strange. It was modified by KASAN. I can't understand this. > Maybe I missed something? Please let me know. Thanks. Looks like KASAN with the extra info ends up writing to io_async_msghdr->free_iov somehow. No idea... For the test case in question, ->free_iov should be NULL when initially allocated, and the io_uring code isn't storing to it. Yet it's non-NULL when you later go and free it, after calling kasan_mempool_poison_object(). -- Jens Axboe
