lkml.org 
[lkml]   [2020]   [Dec]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.19 308/346] ceph: fix race in concurrent __ceph_remove_cap invocations
    Date
    From: Luis Henriques <lhenriques@suse.de>

    commit e5cafce3ad0f8652d6849314d951459c2bff7233 upstream.

    A NULL pointer dereference may occur in __ceph_remove_cap with some of the
    callbacks used in ceph_iterate_session_caps, namely trim_caps_cb and
    remove_session_caps_cb. Those callers hold the session->s_mutex, so they
    are prevented from concurrent execution, but ceph_evict_inode does not.

    Since the callers of this function hold the i_ceph_lock, the fix is simply
    a matter of returning immediately if caps->ci is NULL.

    Cc: stable@vger.kernel.org
    URL: https://tracker.ceph.com/issues/43272
    Suggested-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Luis Henriques <lhenriques@suse.de>
    Reviewed-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ceph/caps.c | 11 +++++++++--
    1 file changed, 9 insertions(+), 2 deletions(-)

    --- a/fs/ceph/caps.c
    +++ b/fs/ceph/caps.c
    @@ -1047,12 +1047,19 @@ void __ceph_remove_cap(struct ceph_cap *
    {
    struct ceph_mds_session *session = cap->session;
    struct ceph_inode_info *ci = cap->ci;
    - struct ceph_mds_client *mdsc =
    - ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;
    + struct ceph_mds_client *mdsc;
    int removed = 0;

    + /* 'ci' being NULL means the remove have already occurred */
    + if (!ci) {
    + dout("%s: cap inode is NULL\n", __func__);
    + return;
    + }
    +
    dout("__ceph_remove_cap %p from %p\n", cap, &ci->vfs_inode);

    + mdsc = ceph_inode_to_client(&ci->vfs_inode)->mdsc;
    +
    /* remove from inode's cap rbtree, and clear auth cap */
    rb_erase(&cap->ci_node, &ci->i_caps);
    if (ci->i_auth_cap == cap)

    \
     
     \ /
      Last update: 2020-12-28 14:36    [W:2.126 / U:0.068 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site