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    Subject[PATCH 4.14 26/40] ceph: fix buffer free while holding i_ceph_lock in fill_inode()
    Date
    [ Upstream commit af8a85a41734f37b67ba8ce69d56b685bee4ac48 ]

    Calling ceph_buffer_put() in fill_inode() may result in freeing the
    i_xattrs.blob buffer while holding the i_ceph_lock. This can be fixed by
    postponing the call until later, when the lock is released.

    The following backtrace was triggered by fstests generic/070.

    BUG: sleeping function called from invalid context at mm/vmalloc.c:2283
    in_atomic(): 1, irqs_disabled(): 0, pid: 3852, name: kworker/0:4
    6 locks held by kworker/0:4/3852:
    #0: 000000004270f6bb ((wq_completion)ceph-msgr){+.+.}, at: process_one_work+0x1b8/0x5f0
    #1: 00000000eb420803 ((work_completion)(&(&con->work)->work)){+.+.}, at: process_one_work+0x1b8/0x5f0
    #2: 00000000be1c53a4 (&s->s_mutex){+.+.}, at: dispatch+0x288/0x1476
    #3: 00000000559cb958 (&mdsc->snap_rwsem){++++}, at: dispatch+0x2eb/0x1476
    #4: 000000000d5ebbae (&req->r_fill_mutex){+.+.}, at: dispatch+0x2fc/0x1476
    #5: 00000000a83d0514 (&(&ci->i_ceph_lock)->rlock){+.+.}, at: fill_inode.isra.0+0xf8/0xf70
    CPU: 0 PID: 3852 Comm: kworker/0:4 Not tainted 5.2.0+ #441
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014
    Workqueue: ceph-msgr ceph_con_workfn
    Call Trace:
    dump_stack+0x67/0x90
    ___might_sleep.cold+0x9f/0xb1
    vfree+0x4b/0x60
    ceph_buffer_release+0x1b/0x60
    fill_inode.isra.0+0xa9b/0xf70
    ceph_fill_trace+0x13b/0xc70
    ? dispatch+0x2eb/0x1476
    dispatch+0x320/0x1476
    ? __mutex_unlock_slowpath+0x4d/0x2a0
    ceph_con_workfn+0xc97/0x2ec0
    ? process_one_work+0x1b8/0x5f0
    process_one_work+0x244/0x5f0
    worker_thread+0x4d/0x3e0
    kthread+0x105/0x140
    ? process_one_work+0x5f0/0x5f0
    ? kthread_park+0x90/0x90
    ret_from_fork+0x3a/0x50

    Signed-off-by: Luis Henriques <lhenriques@suse.com>
    Reviewed-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/ceph/inode.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
    index f2b722f0df5d0..9bda8c7a80a05 100644
    --- a/fs/ceph/inode.c
    +++ b/fs/ceph/inode.c
    @@ -730,6 +730,7 @@ static int fill_inode(struct inode *inode, struct page *locked_page,
    int issued = 0, implemented, new_issued;
    struct timespec mtime, atime, ctime;
    struct ceph_buffer *xattr_blob = NULL;
    + struct ceph_buffer *old_blob = NULL;
    struct ceph_string *pool_ns = NULL;
    struct ceph_cap *new_cap = NULL;
    int err = 0;
    @@ -847,7 +848,7 @@ static int fill_inode(struct inode *inode, struct page *locked_page,
    if ((ci->i_xattrs.version == 0 || !(issued & CEPH_CAP_XATTR_EXCL)) &&
    le64_to_cpu(info->xattr_version) > ci->i_xattrs.version) {
    if (ci->i_xattrs.blob)
    - ceph_buffer_put(ci->i_xattrs.blob);
    + old_blob = ci->i_xattrs.blob;
    ci->i_xattrs.blob = xattr_blob;
    if (xattr_blob)
    memcpy(ci->i_xattrs.blob->vec.iov_base,
    @@ -993,8 +994,8 @@ static int fill_inode(struct inode *inode, struct page *locked_page,
    out:
    if (new_cap)
    ceph_put_cap(mdsc, new_cap);
    - if (xattr_blob)
    - ceph_buffer_put(xattr_blob);
    + ceph_buffer_put(old_blob);
    + ceph_buffer_put(xattr_blob);
    ceph_put_string(pool_ns);
    return err;
    }
    --
    2.20.1


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