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    Subject[PATCH AUTOSEL 4.19 045/141] configfs: fix possible use-after-free in configfs_register_group
    Date
    From: YueHaibing <yuehaibing@huawei.com>

    [ Upstream commit 35399f87e271f7cf3048eab00a421a6519ac8441 ]

    In configfs_register_group(), if create_default_group() failed, we
    forget to unlink the group. It will left a invalid item in the parent list,
    which may trigger the use-after-free issue seen below:

    BUG: KASAN: use-after-free in __list_add_valid+0xd4/0xe0 lib/list_debug.c:26
    Read of size 8 at addr ffff8881ef61ae20 by task syz-executor.0/5996

    CPU: 1 PID: 5996 Comm: syz-executor.0 Tainted: G C 5.0.0+ #5
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
    Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0xa9/0x10e lib/dump_stack.c:113
    print_address_description+0x65/0x270 mm/kasan/report.c:187
    kasan_report+0x149/0x18d mm/kasan/report.c:317
    __list_add_valid+0xd4/0xe0 lib/list_debug.c:26
    __list_add include/linux/list.h:60 [inline]
    list_add_tail include/linux/list.h:93 [inline]
    link_obj+0xb0/0x190 fs/configfs/dir.c:759
    link_group+0x1c/0x130 fs/configfs/dir.c:784
    configfs_register_group+0x56/0x1e0 fs/configfs/dir.c:1751
    configfs_register_default_group+0x72/0xc0 fs/configfs/dir.c:1834
    ? 0xffffffffc1be0000
    iio_sw_trigger_init+0x23/0x1000 [industrialio_sw_trigger]
    do_one_initcall+0xbc/0x47d init/main.c:887
    do_init_module+0x1b5/0x547 kernel/module.c:3456
    load_module+0x6405/0x8c10 kernel/module.c:3804
    __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
    do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x462e99
    Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 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 c7 c1 bc ff ff ff f7 d8 64 89 01 48
    RSP: 002b:00007f494ecbcc58 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
    RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462e99
    RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000003
    RBP: 00007f494ecbcc70 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 00007f494ecbd6bc
    R13: 00000000004bcefa R14: 00000000006f6fb0 R15: 0000000000000004

    Allocated by task 5987:
    set_track mm/kasan/common.c:87 [inline]
    __kasan_kmalloc.constprop.3+0xa0/0xd0 mm/kasan/common.c:497
    kmalloc include/linux/slab.h:545 [inline]
    kzalloc include/linux/slab.h:740 [inline]
    configfs_register_default_group+0x4c/0xc0 fs/configfs/dir.c:1829
    0xffffffffc1bd0023
    do_one_initcall+0xbc/0x47d init/main.c:887
    do_init_module+0x1b5/0x547 kernel/module.c:3456
    load_module+0x6405/0x8c10 kernel/module.c:3804
    __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
    do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

    Freed by task 5987:
    set_track mm/kasan/common.c:87 [inline]
    __kasan_slab_free+0x130/0x180 mm/kasan/common.c:459
    slab_free_hook mm/slub.c:1429 [inline]
    slab_free_freelist_hook mm/slub.c:1456 [inline]
    slab_free mm/slub.c:3003 [inline]
    kfree+0xe1/0x270 mm/slub.c:3955
    configfs_register_default_group+0x9a/0xc0 fs/configfs/dir.c:1836
    0xffffffffc1bd0023
    do_one_initcall+0xbc/0x47d init/main.c:887
    do_init_module+0x1b5/0x547 kernel/module.c:3456
    load_module+0x6405/0x8c10 kernel/module.c:3804
    __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
    do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

    The buggy address belongs to the object at ffff8881ef61ae00
    which belongs to the cache kmalloc-192 of size 192
    The buggy address is located 32 bytes inside of
    192-byte region [ffff8881ef61ae00, ffff8881ef61aec0)
    The buggy address belongs to the page:
    page:ffffea0007bd8680 count:1 mapcount:0 mapping:ffff8881f6c03000 index:0xffff8881ef61a700
    flags: 0x2fffc0000000200(slab)
    raw: 02fffc0000000200 ffffea0007ca4740 0000000500000005 ffff8881f6c03000
    raw: ffff8881ef61a700 000000008010000c 00000001ffffffff 0000000000000000
    page dumped because: kasan: bad access detected

    Memory state around the buggy address:
    ffff8881ef61ad00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ffff8881ef61ad80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
    >ffff8881ef61ae00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ^
    ffff8881ef61ae80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
    ffff8881ef61af00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

    Fixes: 5cf6a51e6062 ("configfs: allow dynamic group creation")
    Reported-by: Hulk Robot <hulkci@huawei.com>
    Signed-off-by: YueHaibing <yuehaibing@huawei.com>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/configfs/dir.c | 17 ++++++++++++-----
    1 file changed, 12 insertions(+), 5 deletions(-)

    diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
    index 39843fa7e11b0..920d350df37b6 100644
    --- a/fs/configfs/dir.c
    +++ b/fs/configfs/dir.c
    @@ -1755,12 +1755,19 @@ int configfs_register_group(struct config_group *parent_group,

    inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
    ret = create_default_group(parent_group, group);
    - if (!ret) {
    - spin_lock(&configfs_dirent_lock);
    - configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
    - spin_unlock(&configfs_dirent_lock);
    - }
    + if (ret)
    + goto err_out;
    +
    + spin_lock(&configfs_dirent_lock);
    + configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
    + spin_unlock(&configfs_dirent_lock);
    + inode_unlock(d_inode(parent));
    + return 0;
    +err_out:
    inode_unlock(d_inode(parent));
    + mutex_lock(&subsys->su_mutex);
    + unlink_group(group);
    + mutex_unlock(&subsys->su_mutex);
    return ret;
    }
    EXPORT_SYMBOL(configfs_register_group);
    --
    2.20.1
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