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    Subject[PATCH AUTOSEL 5.4 35/48] f2fs: fix use-after-free issue
    Date
    From: Li Guifu <bluce.liguifu@huawei.com>

    [ Upstream commit 99c787cfd2bd04926f1f553b30bd7dcea2caaba1 ]

    During umount, f2fs_put_super() unregisters procfs entries after
    f2fs_destroy_segment_manager(), it may cause use-after-free
    issue when umount races with procfs accessing, fix it by relocating
    f2fs_unregister_sysfs().

    [Chao Yu: change commit title/message a bit]

    Signed-off-by: Li Guifu <bluce.liguifu@huawei.com>
    Reviewed-by: Chao Yu <yuchao0@huawei.com>
    Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/f2fs/super.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
    index f4b882ee48ddf..fa461db696e79 100644
    --- a/fs/f2fs/super.c
    +++ b/fs/f2fs/super.c
    @@ -1075,6 +1075,9 @@ static void f2fs_put_super(struct super_block *sb)
    int i;
    bool dropped;

    + /* unregister procfs/sysfs entries in advance to avoid race case */
    + f2fs_unregister_sysfs(sbi);
    +
    f2fs_quota_off_umount(sb);

    /* prevent remaining shrinker jobs */
    @@ -1138,8 +1141,6 @@ static void f2fs_put_super(struct super_block *sb)

    kvfree(sbi->ckpt);

    - f2fs_unregister_sysfs(sbi);
    -
    sb->s_fs_info = NULL;
    if (sbi->s_chksum_driver)
    crypto_free_shash(sbi->s_chksum_driver);
    --
    2.25.1
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