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    Subject[PATCH AUTOSEL 4.19 123/123] ocfs2: fix potential use after free
    Date
    From: Pan Bian <bianpan2016@163.com>

    [ Upstream commit 164f7e586739d07eb56af6f6d66acebb11f315c8 ]

    ocfs2_get_dentry() calls iput(inode) to drop the reference count of
    inode, and if the reference count hits 0, inode is freed. However, in
    this function, it then reads inode->i_generation, which may result in a
    use after free bug. Move the put operation later.

    Link: http://lkml.kernel.org/r/1543109237-110227-1-git-send-email-bianpan2016@163.com
    Fixes: 781f200cb7a("ocfs2: Remove masklog ML_EXPORT.")
    Signed-off-by: Pan Bian <bianpan2016@163.com>
    Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: Mark Fasheh <mark@fasheh.com>
    Cc: Joel Becker <jlbec@evilplan.org>
    Cc: Junxiao Bi <junxiao.bi@oracle.com>
    Cc: Joseph Qi <jiangqi903@gmail.com>
    Cc: Changwei Ge <ge.changwei@h3c.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/ocfs2/export.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
    index 9f88188060db..4bf8d5854b27 100644
    --- a/fs/ocfs2/export.c
    +++ b/fs/ocfs2/export.c
    @@ -125,10 +125,10 @@ static struct dentry *ocfs2_get_dentry(struct super_block *sb,

    check_gen:
    if (handle->ih_generation != inode->i_generation) {
    - iput(inode);
    trace_ocfs2_get_dentry_generation((unsigned long long)blkno,
    handle->ih_generation,
    inode->i_generation);
    + iput(inode);
    result = ERR_PTR(-ESTALE);
    goto bail;
    }
    --
    2.17.1
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