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    Subject[PATCH AUTOSEL for 4.4 137/162] ocfs2/acl: use 'ip_xattr_sem' to protect getting extended attribute
    Date
    From: piaojun <piaojun@huawei.com>

    [ Upstream commit 16c8d569f5704a84164f30ff01b29879f3438065 ]

    The race between *set_acl and *get_acl will cause getting incomplete
    xattr data as below:

    processA processB

    ocfs2_set_acl
    ocfs2_xattr_set
    __ocfs2_xattr_set_handle

    ocfs2_get_acl_nolock
    ocfs2_xattr_get_nolock:

    processB may get incomplete xattr data if processA hasn't set_acl done.

    So we should use 'ip_xattr_sem' to protect getting extended attribute in
    ocfs2_get_acl_nolock(), as other processes could be changing it
    concurrently.

    Link: http://lkml.kernel.org/r/5A5DDCFF.7030001@huawei.com
    Signed-off-by: Jun Piao <piaojun@huawei.com>
    Reviewed-by: Alex Chen <alex.chen@huawei.com>
    Cc: Mark Fasheh <mfasheh@versity.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 <alexander.levin@microsoft.com>
    ---
    fs/ocfs2/acl.c | 6 ++++++
    fs/ocfs2/xattr.c | 2 ++
    2 files changed, 8 insertions(+)

    diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
    index 164307b99405..1e0d8da0d3cd 100644
    --- a/fs/ocfs2/acl.c
    +++ b/fs/ocfs2/acl.c
    @@ -314,7 +314,9 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
    return ERR_PTR(ret);
    }

    + down_read(&OCFS2_I(inode)->ip_xattr_sem);
    acl = ocfs2_get_acl_nolock(inode, type, di_bh);
    + up_read(&OCFS2_I(inode)->ip_xattr_sem);

    ocfs2_inode_unlock(inode, 0);
    brelse(di_bh);
    @@ -333,7 +335,9 @@ int ocfs2_acl_chmod(struct inode *inode, struct buffer_head *bh)
    if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
    return 0;

    + down_read(&OCFS2_I(inode)->ip_xattr_sem);
    acl = ocfs2_get_acl_nolock(inode, ACL_TYPE_ACCESS, bh);
    + up_read(&OCFS2_I(inode)->ip_xattr_sem);
    if (IS_ERR(acl) || !acl)
    return PTR_ERR(acl);
    ret = __posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
    @@ -364,8 +368,10 @@ int ocfs2_init_acl(handle_t *handle,

    if (!S_ISLNK(inode->i_mode)) {
    if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
    + down_read(&OCFS2_I(dir)->ip_xattr_sem);
    acl = ocfs2_get_acl_nolock(dir, ACL_TYPE_DEFAULT,
    dir_bh);
    + up_read(&OCFS2_I(dir)->ip_xattr_sem);
    if (IS_ERR(acl))
    return PTR_ERR(acl);
    }
    diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
    index d2b7192c0937..7f78daf88f35 100644
    --- a/fs/ocfs2/xattr.c
    +++ b/fs/ocfs2/xattr.c
    @@ -639,9 +639,11 @@ int ocfs2_calc_xattr_init(struct inode *dir,
    si->value_len);

    if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
    + down_read(&OCFS2_I(dir)->ip_xattr_sem);
    acl_len = ocfs2_xattr_get_nolock(dir, dir_bh,
    OCFS2_XATTR_INDEX_POSIX_ACL_DEFAULT,
    "", NULL, 0);
    + up_read(&OCFS2_I(dir)->ip_xattr_sem);
    if (acl_len > 0) {
    a_size = ocfs2_xattr_entry_real_size(0, acl_len);
    if (S_ISDIR(mode))
    --
    2.15.1
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