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    Subject[PATCH 4.14 422/496] f2fs: fix to check extent cache in f2fs_drop_extent_tree
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Chao Yu <yuchao0@huawei.com>

    [ Upstream commit bf617f7a92edc6bb2909db2bfa4576f50b280ee5 ]

    If noextent_cache mount option is on, we will never initialize extent tree
    in inode, but still we're going to access it in f2fs_drop_extent_tree,
    result in kernel panic as below:

    BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
    IP: _raw_write_lock+0xc/0x30
    Call Trace:
    ? f2fs_drop_extent_tree+0x41/0x70 [f2fs]
    f2fs_fallocate+0x5a0/0xdd0 [f2fs]
    ? common_file_perm+0x47/0xc0
    ? apparmor_file_permission+0x1a/0x20
    vfs_fallocate+0x15b/0x290
    SyS_fallocate+0x44/0x70
    do_syscall_64+0x6e/0x160
    entry_SYSCALL64_slow_path+0x25/0x25

    This patch fixes to check extent cache status before using in
    f2fs_drop_extent_tree.

    Signed-off-by: Chao Yu <yuchao0@huawei.com>
    Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/f2fs/extent_cache.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/fs/f2fs/extent_cache.c
    +++ b/fs/f2fs/extent_cache.c
    @@ -706,6 +706,9 @@ void f2fs_drop_extent_tree(struct inode
    struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
    struct extent_tree *et = F2FS_I(inode)->extent_tree;

    + if (!f2fs_may_extent_tree(inode))
    + return;
    +
    set_inode_flag(inode, FI_NO_EXTENT);

    write_lock(&et->lock);

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