================================================================== BUG: KASAN: use-after-free in gsm_cleanup_mux+0x660/0x738 drivers/tty/n_gsm.c:2397 Read of size 4 at addr ffff0000c8b4a00c by task syz-executor242/3967 CPU: 0 PID: 3967 Comm: syz-executor242 Not tainted 5.15.113-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023 Call trace: dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106 print_address_description+0x7c/0x3f0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:434 [inline] kasan_report+0x174/0x1e4 mm/kasan/report.c:451 __asan_report_load4_noabort+0x44/0x50 mm/kasan/report_generic.c:308 gsm_cleanup_mux+0x660/0x738 drivers/tty/n_gsm.c:2397 gsm_config drivers/tty/n_gsm.c:2653 [inline] gsmld_ioctl+0xa48/0x13d8 drivers/tty/n_gsm.c:2986 tty_ioctl+0x954/0xdf4 drivers/tty/tty_io.c:2816 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Allocated by task 3962: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] ____kasan_kmalloc+0xbc/0xfc mm/kasan/common.c:513 __kasan_kmalloc+0x10/0x1c mm/kasan/common.c:522 kasan_kmalloc include/linux/kasan.h:264 [inline] kmem_cache_alloc_trace+0x27c/0x47c mm/slub.c:3247 kmalloc include/linux/slab.h:591 [inline] kzalloc include/linux/slab.h:721 [inline] gsm_dlci_alloc+0x60/0x340 drivers/tty/n_gsm.c:1932 gsm_activate_mux+0x30/0x300 drivers/tty/n_gsm.c:2438 gsm_config drivers/tty/n_gsm.c:2677 [inline] gsmld_ioctl+0xc1c/0x13d8 drivers/tty/n_gsm.c:2986 tty_ioctl+0x954/0xdf4 drivers/tty/tty_io.c:2816 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Freed by task 3962: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track+0x4c/0x84 mm/kasan/common.c:46 kasan_set_free_info+0x28/0x4c mm/kasan/generic.c:360 ____kasan_slab_free+0x118/0x164 mm/kasan/common.c:366 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:230 [inline] slab_free_hook mm/slub.c:1705 [inline] slab_free_freelist_hook+0x128/0x1ec mm/slub.c:1731 slab_free mm/slub.c:3499 [inline] kfree+0x178/0x410 mm/slub.c:4559 gsm_dlci_free+0x11c/0x168 drivers/tty/n_gsm.c:1978 tty_port_destructor drivers/tty/tty_port.c:265 [inline] kref_put include/linux/kref.h:65 [inline] tty_port_put+0x140/0x1bc drivers/tty/tty_port.c:273 dlci_put drivers/tty/n_gsm.c:1988 [inline] gsm_dlci_release drivers/tty/n_gsm.c:2021 [inline] gsm_cleanup_mux+0x488/0x738 drivers/tty/n_gsm.c:2415 gsm_config drivers/tty/n_gsm.c:2653 [inline] gsmld_ioctl+0xa48/0x13d8 drivers/tty/n_gsm.c:2986 tty_ioctl+0x954/0xdf4 drivers/tty/tty_io.c:2816 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 The buggy address belongs to the object at ffff0000c8b4a000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 12 bytes inside of 2048-byte region [ffff0000c8b4a000, ffff0000c8b4a800) The buggy address belongs to the page: page:0000000003bf807d refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x108b48 head:0000000003bf807d order:3 compound_mapcount:0 compound_pincount:0 flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff) raw: 05ffc00000010200 0000000000000000 dead000000000122 ffff0000c0002900 raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff0000c8b49f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff0000c8b49f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff0000c8b4a000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff0000c8b4a080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff0000c8b4a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Unable to handle kernel paging request at virtual address dfff80000000000a Mem abort info: ESR = 0x0000000096000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x06: level 2 translation fault Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 [dfff80000000000a] address between user and kernel address ranges Internal error: Oops: 96000006 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 3967 Comm: syz-executor242 Tainted: G B 5.15.113-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023 pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : tty_write_room+0x48/0x8c drivers/tty/tty_ioctl.c:78 lr : tty_write_room+0x3c/0x8c drivers/tty/tty_ioctl.c:78 sp : ffff80001cdc7810 x29: ffff80001cdc7810 x28: 0000000000000001 x27: dfff800000000000 x26: 1ffff000039b8f14 x25: 0000000000000000 x24: 1fffe00019984cc0 x23: dfff800000000000 x22: 0000000000000f7a x21: dfff800000000000 x20: 0000000000000050 x19: ffff0000c7838a00 x18: 0000000000000000 x17: ff8080000b3ef030 x16: 0000000000000000 x15: ffff80000b3ef030 x14: 0000000000000002 x13: ffffffffffffffff x12: 0000000000000000 x11: ff8080000b3d191c x10: 0000000000000000 x9 : ffff80001842e390 x8 : 000000000000000a x7 : 0000000000000000 x6 : ffff800008268c6c x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff80000b3d1934 x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000000 Call trace: tty_write_room+0x48/0x8c drivers/tty/tty_ioctl.c:78 gsmld_output+0x4c/0x1d0 drivers/tty/n_gsm.c:2698 gsm_send+0x4dc/0x798 drivers/tty/n_gsm.c:707 gsm_command drivers/tty/n_gsm.c:736 [inline] gsm_dlci_begin_close drivers/tty/n_gsm.c:1801 [inline] gsm_cleanup_mux+0x1a0/0x738 drivers/tty/n_gsm.c:2398 gsm_config drivers/tty/n_gsm.c:2653 [inline] gsmld_ioctl+0xa48/0x13d8 drivers/tty/n_gsm.c:2986 tty_ioctl+0x954/0xdf4 drivers/tty/tty_io.c:2816 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Code: 9753d81a f9400288 91014114 d343fe88 (38756908) ---[ end trace abbff69097bf988f ]--- ---------------- Code disassembly (best guess): 0: 9753d81a bl 0xfffffffffd4f6068 4: f9400288 ldr x8, [x20] 8: 91014114 add x20, x8, #0x50 c: d343fe88 lsr x8, x20, #3 * 10: 38756908 ldrb w8, [x8, x21] <-- trapping instruction