This patch fixes a possible use after free if tracing for the specific event is enabled. To avoid the use after free we introduce a out_put label like all other user lock specific requests and safe in a boolean to do a put or not which depends on the execution path of dlm_user_request().

Cc: stable@vger.kernel.org Fixes: 7a3de7324c2b ("fs: dlm: trace user space callbacks") Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Alexander Aring aahringo@redhat.com --- fs/dlm/lock.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c index c830feb26384..94a72ede5764 100644 --- a/fs/dlm/lock.c +++ b/fs/dlm/lock.c @@ -5835,6 +5835,7 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua, { struct dlm_lkb *lkb; struct dlm_args args; + bool do_put = true; int error;

dlm_lock_recovery(ls); @@ -5851,9 +5852,8 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua, ua->lksb.sb_lvbptr = kzalloc(DLM_USER_LVB_LEN, GFP_NOFS); if (!ua->lksb.sb_lvbptr) { kfree(ua); - __put_lkb(ls, lkb); error = -ENOMEM; - goto out_trace_end; + goto out_put; } } #ifdef CONFIG_DLM_DEPRECATED_API @@ -5867,8 +5867,7 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua, kfree(ua->lksb.sb_lvbptr); ua->lksb.sb_lvbptr = NULL; kfree(ua); - __put_lkb(ls, lkb); - goto out_trace_end; + goto out_put; }

/* After ua is attached to lkb it will be freed by dlm_free_lkb(). @@ -5887,8 +5886,7 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua, error = 0; fallthrough; default: - __put_lkb(ls, lkb); - goto out_trace_end; + goto out_put; }

/* add this new lkb to the per-process list of locks */ @@ -5896,8 +5894,11 @@ int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua, hold_lkb(lkb); list_add_tail(&lkb->lkb_ownqueue, &ua->proc->locks); spin_unlock(&ua->proc->locks_spin); - out_trace_end: + do_put = false; + out_put: trace_dlm_lock_end(ls, lkb, name, namelen, mode, flags, error, false); + if (do_put) + __put_lkb(ls, lkb); out: dlm_unlock_recovery(ls); return error;