Messages in this thread | | | From | (Eric W. Biederman) | Date | Fri, 20 Aug 2021 08:44:32 -0500 | Subject | Re: [syzbot] KASAN: use-after-free Write in dec_rlimit_ucounts |
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Alexey Gladkov <legion@kernel.org> writes:
> On Thu, Aug 19, 2021 at 01:32:22PM -0700, syzbot wrote: >> syzbot has found a reproducer for the following issue on: >> >> HEAD commit: d6d09a694205 Merge tag 'for-5.14-rc6-tag' of git://git.ker.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=16c8081e300000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=f61012d0b1cd846f >> dashboard link: https://syzkaller.appspot.com/bug?extid=01985d7909f9468f013c >> compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d0ec1e300000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1516c341300000 >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+01985d7909f9468f013c@syzkaller.appspotmail.com >> >> RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000004ca4cc >> RBP: 00000000004ca4c0 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000001 R11: 0000000000000246 R12: 00000000004ca4cc >> R13: 00007fffffe0b62f R14: 00007f1054173400 R15: 0000000000022000 >> ================================================================== >> BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline] >> BUG: KASAN: use-after-free in atomic64_add_return include/asm-generic/atomic-instrumented.h:640 [inline] >> BUG: KASAN: use-after-free in atomic_long_add_return include/asm-generic/atomic-long.h:59 [inline] >> BUG: KASAN: use-after-free in dec_rlimit_ucounts+0x88/0x170 kernel/ucount.c:279 >> Write of size 8 at addr ffff888025b8ef80 by task syz-executor668/8707 >> >> CPU: 1 PID: 8707 Comm: syz-executor668 Not tainted 5.14.0-rc6-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:88 [inline] >> dump_stack_lvl+0x1ae/0x29f lib/dump_stack.c:105 >> print_address_description+0x66/0x3b0 mm/kasan/report.c:233 >> __kasan_report mm/kasan/report.c:419 [inline] >> kasan_report+0x163/0x210 mm/kasan/report.c:436 >> check_region_inline mm/kasan/generic.c:135 [inline] >> kasan_check_range+0x2b5/0x2f0 mm/kasan/generic.c:189 >> instrument_atomic_read_write include/linux/instrumented.h:101 [inline] >> atomic64_add_return include/asm-generic/atomic-instrumented.h:640 [inline] >> atomic_long_add_return include/asm-generic/atomic-long.h:59 [inline] >> dec_rlimit_ucounts+0x88/0x170 kernel/ucount.c:279 >> release_task+0x2d3/0x1590 kernel/exit.c:191 > > void release_task(struct task_struct *p) > { > ... > /* don't need to get the RCU readlock here - the process is dead and > * can't be modifying its own credentials. But shut RCU-lockdep up */ > rcu_read_lock(); > dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); > rcu_read_unlock(); > ... > } > > It looks like the ucounts have been released before this in the put_cred_rcu().
That should not be.
After that in release_task there is:
put_task_struct_rcu_user delayed_put_task_struct put_task_struct __put_task_struct exit_creds put_cred __put_cred put_cred_rcu put_ucounts
So there very much should be a valid cred reference at that point.
>> exit_notify kernel/exit.c:699 [inline] >> do_exit+0x1aa2/0x2510 kernel/exit.c:845 >> do_group_exit+0x168/0x2d0 kernel/exit.c:922 >> get_signal+0x16b0/0x2080 kernel/signal.c:2808 >> arch_do_signal_or_restart+0x8e/0x6d0 arch/x86/kernel/signal.c:865 >> handle_signal_work kernel/entry/common.c:148 [inline] >> exit_to_user_mode_loop kernel/entry/common.c:172 [inline] >> exit_to_user_mode_prepare+0x191/0x220 kernel/entry/common.c:209 >> __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] >> syscall_exit_to_user_mode+0x26/0x60 kernel/entry/common.c:302 >> do_syscall_64+0x4c/0xb0 arch/x86/entry/common.c:86 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> RIP: 0033:0x445a69 >> Code: Unable to access opcode bytes at RIP 0x445a3f. >> RSP: 002b:00007f1054173318 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca >> RAX: fffffffffffffff2 RBX: 00000000004ca4c8 RCX: 0000000000445a69 >> RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000004ca4cc >> RBP: 00000000004ca4c0 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000001 R11: 0000000000000246 R12: 00000000004ca4cc >> R13: 00007fffffe0b62f R14: 00007f1054173400 R15: 0000000000022000 >> >> Allocated by task 8441: >> 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+0xc4/0xf0 mm/kasan/common.c:513 >> kasan_kmalloc include/linux/kasan.h:264 [inline] >> kmem_cache_alloc_trace+0x96/0x340 mm/slub.c:2986 >> kmalloc include/linux/slab.h:591 [inline] >> kzalloc include/linux/slab.h:721 [inline] >> alloc_ucounts+0x1b1/0x5d0 kernel/ucount.c:173 >> set_cred_ucounts+0x220/0x2d0 kernel/cred.c:684 >> __sys_setresuid+0x6d5/0x920 kernel/sys.c:702 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> Freed by task 13: >> kasan_save_stack mm/kasan/common.c:38 [inline] >> kasan_set_track+0x3d/0x70 mm/kasan/common.c:46 >> kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360 >> ____kasan_slab_free+0x109/0x150 mm/kasan/common.c:366 >> kasan_slab_free include/linux/kasan.h:230 [inline] >> slab_free_hook mm/slub.c:1628 [inline] >> slab_free_freelist_hook+0x1d8/0x290 mm/slub.c:1653 >> slab_free mm/slub.c:3213 [inline] >> kfree+0xcf/0x2e0 mm/slub.c:4267 >> put_ucounts+0x15c/0x1a0 kernel/ucount.c:207 >> put_cred_rcu+0x221/0x400 kernel/cred.c:124 >> rcu_do_batch kernel/rcu/tree.c:2550 [inline] >> rcu_core+0x906/0x14b0 kernel/rcu/tree.c:2785 >> __do_softirq+0x372/0x783 kernel/softirq.c:558 >> >> Last potentially related work creation: >> kasan_save_stack+0x27/0x50 mm/kasan/common.c:38 >> kasan_record_aux_stack+0xee/0x120 mm/kasan/generic.c:348 >> insert_work+0x54/0x400 kernel/workqueue.c:1332 >> __queue_work+0x928/0xc60 kernel/workqueue.c:1498 >> queue_work_on+0x111/0x200 kernel/workqueue.c:1525 >> queue_work include/linux/workqueue.h:507 [inline] >> call_usermodehelper_exec+0x283/0x470 kernel/umh.c:435 >> kobject_uevent_env+0x1337/0x1700 lib/kobject_uevent.c:618 >> device_add+0x1073/0x1790 drivers/base/core.c:3336 >> device_create_groups_vargs drivers/base/core.c:4014 [inline] >> device_create+0x241/0x2d0 drivers/base/core.c:4056 >> vc_allocate+0x66a/0x780 drivers/tty/vt/vt.c:1157 >> con_install+0x9f/0x880 drivers/tty/vt/vt.c:3342 >> tty_driver_install_tty drivers/tty/tty_io.c:1315 [inline] >> tty_init_dev+0xc6/0x4c0 drivers/tty/tty_io.c:1429 >> tty_open_by_driver drivers/tty/tty_io.c:2098 [inline] >> tty_open+0x89a/0xdd0 drivers/tty/tty_io.c:2146 >> chrdev_open+0x53b/0x5f0 fs/char_dev.c:414 >> do_dentry_open+0x7cb/0x1020 fs/open.c:826 >> do_open fs/namei.c:3374 [inline] >> path_openat+0x27e7/0x36b0 fs/namei.c:3507 >> do_filp_open+0x253/0x4d0 fs/namei.c:3534 >> do_sys_openat2+0x124/0x460 fs/open.c:1204 >> do_sys_open fs/open.c:1220 [inline] >> __do_sys_open fs/open.c:1228 [inline] >> __se_sys_open fs/open.c:1224 [inline] >> __x64_sys_open+0x221/0x270 fs/open.c:1224 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> Second to last potentially related work creation: >> kasan_save_stack+0x27/0x50 mm/kasan/common.c:38 >> kasan_record_aux_stack+0xee/0x120 mm/kasan/generic.c:348 >> insert_work+0x54/0x400 kernel/workqueue.c:1332 >> __queue_work+0x928/0xc60 kernel/workqueue.c:1498 >> queue_work_on+0x111/0x200 kernel/workqueue.c:1525 >> queue_work include/linux/workqueue.h:507 [inline] >> call_usermodehelper_exec+0x283/0x470 kernel/umh.c:435 >> kobject_uevent_env+0x1337/0x1700 lib/kobject_uevent.c:618 >> kobject_synth_uevent+0x3bf/0x900 lib/kobject_uevent.c:208 >> uevent_store+0x20/0x60 drivers/base/core.c:2372 >> kernfs_fop_write_iter+0x3b6/0x510 fs/kernfs/file.c:296 >> call_write_iter include/linux/fs.h:2114 [inline] >> new_sync_write fs/read_write.c:518 [inline] >> vfs_write+0xa39/0xc90 fs/read_write.c:605 >> ksys_write+0x171/0x2a0 fs/read_write.c:658 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> The buggy address belongs to the object at ffff888025b8ef00 >> which belongs to the cache kmalloc-192 of size 192 >> The buggy address is located 128 bytes inside of >> 192-byte region [ffff888025b8ef00, ffff888025b8efc0) >> The buggy address belongs to the page: >> page:ffffea000096e380 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25b8e >> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff) >> raw: 00fff00000000200 ffffea00005dac80 0000000c0000000c ffff888011041a00 >> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> page_owner tracks the page as allocated >> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 9979944008, free_ts 0 >> prep_new_page mm/page_alloc.c:2436 [inline] >> get_page_from_freelist+0x779/0xa30 mm/page_alloc.c:4169 >> __alloc_pages+0x26c/0x5f0 mm/page_alloc.c:5391 >> alloc_page_interleave+0x22/0x1c0 mm/mempolicy.c:2119 >> alloc_slab_page mm/slub.c:1691 [inline] >> allocate_slab+0xf1/0x540 mm/slub.c:1831 >> new_slab mm/slub.c:1894 [inline] >> new_slab_objects mm/slub.c:2640 [inline] >> ___slab_alloc+0x1cf/0x350 mm/slub.c:2803 >> __slab_alloc mm/slub.c:2843 [inline] >> slab_alloc_node mm/slub.c:2925 [inline] >> slab_alloc mm/slub.c:2967 [inline] >> kmem_cache_alloc_trace+0x29d/0x340 mm/slub.c:2984 >> kmalloc include/linux/slab.h:591 [inline] >> kzalloc include/linux/slab.h:721 [inline] >> call_usermodehelper_setup+0x8a/0x260 kernel/umh.c:365 >> kobject_uevent_env+0x1311/0x1700 lib/kobject_uevent.c:614 >> device_add+0x1073/0x1790 drivers/base/core.c:3336 >> __video_register_device+0x37fc/0x4580 drivers/media/v4l2-core/v4l2-dev.c:1036 >> video_register_device include/media/v4l2-dev.h:384 [inline] >> vivid_create_devnodes drivers/media/test-drivers/vivid/vivid-core.c:1585 [inline] >> vivid_create_instance+0x85df/0xac90 drivers/media/test-drivers/vivid/vivid-core.c:1946 >> vivid_probe+0x9a/0x140 drivers/media/test-drivers/vivid/vivid-core.c:2001 >> platform_probe+0x130/0x1b0 drivers/base/platform.c:1427 >> call_driver_probe+0x96/0x250 drivers/base/dd.c:517 >> really_probe+0x223/0x9b0 drivers/base/dd.c:595 >> __driver_probe_device+0x1f8/0x3e0 drivers/base/dd.c:747 >> page_owner free stack trace missing >> >> Memory state around the buggy address: >> ffff888025b8ee80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >> ffff888025b8ef00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> >ffff888025b8ef80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >> ^ >> ffff888025b8f000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> ffff888025b8f080: 00 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 >> ================================================================== >>
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