Hi Kernel Maintainers, I hit the following report while testing current upstream kernel:
KASAN: slab-use-after-free in port_fops_splice_write I reproduced this on commit: e8c2f9fdadee7cbc75134dc463c1e0d856d6e5c7 (May 25 2026) The reproducer and .config files are here. https://gist.github.com/shuangpengbai/d21a9a20a05cd840b99ea90101888879 I'm happy to test debug patches or provide additional information. Reported-by: Shuangpeng Bai <[email protected]> [ 78.120298][ T8329] BUG: KASAN: slab-use-after-free in port_fops_splice_write (drivers/char/virtio_console.c:922) [ 78.121417][ T8329] Read of size 8 at addr ffff8881158d7020 by task virtconsole_spl/8329 [ 78.122247][ T8329] [ 78.122502][ T8329] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 78.122505][ T8329] Call Trace: [ 78.122508][ T8329] <TASK> [ 78.122510][ T8329] dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120) [ 78.123695][ T8329] print_report (mm/kasan/report.c:378 mm/kasan/report.c:482) [ 78.123714][ T8329] kasan_report (mm/kasan/report.c:595) [ 78.123722][ T8329] port_fops_splice_write (drivers/char/virtio_console.c:922) [ 78.123754][ T8329] do_splice (fs/splice.c:936 fs/splice.c:1349) [ 78.123773][ T8329] __se_sys_splice (fs/splice.c:1431 fs/splice.c:1634 fs/splice.c:1616) [ 78.123782][ T8329] do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) [ 78.123795][ T8329] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) [ 78.123799][ T8329] RIP: 0033:0x7f875ebb2f29 [ 78.123805][ T8329] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 37 8f 0d 00 f7 d8 64 89 01 48 [ 78.123808][ T8329] RSP: 002b:00007ffdd2abad88 EFLAGS: 00000206 ORIG_RAX: 0000000000000113 [ 78.123815][ T8329] RAX: ffffffffffffffda RBX: 00007f875eabb6c0 RCX: 00007f875ebb2f29 [ 78.123818][ T8329] RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000004 [ 78.123819][ T8329] RBP: 00007ffdd2abbdb0 R08: 0000000000001000 R09: 0000000000000000 [ 78.123822][ T8329] R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 [ 78.123823][ T8329] R13: 00007ffdd2abbdd7 R14: 0000000000000000 R15: 0000000000000000 [ 78.123828][ T8329] </TASK> [ 78.123830][ T8329] [ 78.144834][ T8329] Freed by task 8329 on cpu 1 at 78.116533s: [ 78.145445][ T8329] kasan_save_track (mm/kasan/common.c:57 mm/kasan/common.c:78) [ 78.145926][ T8329] kasan_save_free_info (mm/kasan/generic.c:584) [ 78.146445][ T8329] __kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285) [ 78.146936][ T8329] kfree (include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566) [ 78.147342][ T8329] vp_del_vqs (drivers/virtio/virtio_pci_common.c:259 drivers/virtio/virtio_pci_common.c:285) [ 78.147779][ T8329] remove_vqs (drivers/char/virtio_console.c:1895) [ 78.148226][ T8329] virtcons_remove (drivers/char/virtio_console.c:1939) [ 78.148717][ T8329] virtio_dev_remove (drivers/virtio/virtio.c:375) [ 78.149220][ T8329] device_release_driver_internal (drivers/base/dd.c:619 drivers/base/dd.c:1352 drivers/base/dd.c:1375) [ 78.149821][ T8329] unbind_store (drivers/base/bus.c:244) [ 78.150261][ T8329] kernfs_fop_write_iter (fs/kernfs/file.c:352) [ 78.150762][ T8329] vfs_write (fs/read_write.c:595 fs/read_write.c:688) [ 78.151167][ T8329] ksys_write (fs/read_write.c:740) [ 78.151579][ T8329] do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) [ 78.152019][ T8329] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) [ 78.152581][ T8329] [ 78.152811][ T8329] The buggy address belongs to the object at ffff8881158d7000 [ 78.152811][ T8329] which belongs to the cache kmalloc-256 of size 256 [ 78.154115][ T8329] The buggy address is located 32 bytes inside of [ 78.154115][ T8329] freed 256-byte region [ffff8881158d7000, ffff8881158d7100) [ 78.155397][ T8329] Best, Shuangpeng
