================================================================== BUG: KASAN: slab-use-after-free in ppp_async_encode drivers/net/ppp/ppp_async.c:579 [inline] BUG: KASAN: slab-use-after-free in ppp_async_push+0xa68/0x1650 drivers/net/ppp/ppp_async.c:675 Read of size 1 at addr ffff0000d4ac4000 by task syz.1.100/7166 CPU: 1 UID: 0 PID: 7166 Comm: syz.1.100 Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 print_address_description+0xa8/0x238 mm/kasan/report.c:378 print_report+0x68/0x84 mm/kasan/report.c:482 kasan_report+0xb0/0x110 mm/kasan/report.c:595 __asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378 ppp_async_encode drivers/net/ppp/ppp_async.c:579 [inline] ppp_async_push+0xa68/0x1650 drivers/net/ppp/ppp_async.c:675 ppp_async_send+0xb0/0x114 drivers/net/ppp/ppp_async.c:634 ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2286 [inline] ppp_input+0x224/0x844 drivers/net/ppp/ppp_generic.c:2310 pppoe_rcv_core+0xb4/0x2d8 drivers/net/ppp/pppoe.c:376 sk_backlog_rcv include/net/sock.h:1148 [inline] __release_sock+0x19c/0x39c net/core/sock.c:3194 release_sock+0x60/0x1ac net/core/sock.c:3748 pppoe_sendmsg+0x124/0x5fc drivers/net/ppp/pppoe.c:904 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg net/socket.c:729 [inline] ____sys_sendmsg+0x490/0x7b8 net/socket.c:2614 ___sys_sendmsg+0x204/0x278 net/socket.c:2668 __sys_sendmmsg+0x1f4/0x548 net/socket.c:2757 __do_sys_sendmmsg net/socket.c:2784 [inline] __se_sys_sendmmsg net/socket.c:2781 [inline] __arm64_sys_sendmmsg+0xa0/0xbc net/socket.c:2781 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 Allocated by task 6174: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x40/0x78 mm/kasan/common.c:68 kasan_save_alloc_info+0x44/0x54 mm/kasan/generic.c:562 poison_kmalloc_redzone mm/kasan/common.c:388 [inline] __kasan_kmalloc+0x9c/0xb4 mm/kasan/common.c:405 kasan_kmalloc include/linux/kasan.h:260 [inline] __kmalloc_cache_noprof+0x2a4/0x3fc mm/slub.c:4396 kmalloc_noprof include/linux/slab.h:905 [inline] slab_free_hook mm/slub.c:2369 [inline] slab_free mm/slub.c:4680 [inline] kmem_cache_free+0x168/0x550 mm/slub.c:4782 file_free+0x148/0x208 fs/file_table.c:-1 __fput+0x540/0x75c fs/file_table.c:481 fput_close_sync+0x100/0x224 fs/file_table.c:573 __do_sys_close fs/open.c:1587 [inline] __se_sys_close fs/open.c:1572 [inline] __arm64_sys_close+0x7c/0x118 fs/open.c:1572 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 Freed by task 6982: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x40/0x78 mm/kasan/common.c:68 kasan_save_free_info+0x58/0x70 mm/kasan/generic.c:576 poison_slab_object mm/kasan/common.c:243 [inline] __kasan_slab_free+0x74/0x98 mm/kasan/common.c:275 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2417 [inline] slab_free mm/slub.c:4680 [inline] kfree+0x17c/0x474 mm/slub.c:4879 slab_free_after_rcu_debug+0x78/0x2f4 mm/slub.c:4717 rcu_do_batch kernel/rcu/tree.c:2605 [inline] rcu_core+0x840/0x17d0 kernel/rcu/tree.c:2861 rcu_core_si+0x10/0x1c kernel/rcu/tree.c:2878 handle_softirqs+0x328/0xc88 kernel/softirq.c:579 __do_softirq+0x14/0x20 kernel/softirq.c:613 Last potentially related work creation: kasan_save_stack+0x40/0x6c mm/kasan/common.c:47 kasan_record_aux_stack+0xb0/0xc8 mm/kasan/generic.c:548 __call_rcu_common kernel/rcu/tree.c:3123 [inline] call_rcu+0x100/0x978 kernel/rcu/tree.c:3243 slab_free_hook mm/slub.c:2381 [inline] slab_free mm/slub.c:4680 [inline] kmem_cache_free+0x368/0x550 mm/slub.c:4782 file_free+0x148/0x208 fs/file_table.c:-1 __fput+0x540/0x75c fs/file_table.c:481 fput_close_sync+0x100/0x224 fs/file_table.c:573 __do_sys_close fs/open.c:1587 [inline] __se_sys_close fs/open.c:1572 [inline] __arm64_sys_close+0x7c/0x118 fs/open.c:1572 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 The buggy address belongs to the object at ffff0000d4ac4000 which belongs to the cache kmalloc-32 of size 32 The buggy address is located 0 bytes inside of freed 32-byte region [ffff0000d4ac4000, ffff0000d4ac4020) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x114ac4 anon flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff) page_type: f5(slab) raw: 05ffc00000000000 ffff0000c0001780 0000000000000000 dead000000000001 raw: 0000000000000000 0000000000400040 00000000f5000000 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff0000d4ac3f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff0000d4ac3f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff0000d4ac4000: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc ^ ffff0000d4ac4080: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc ffff0000d4ac4100: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc ==================================================================