[PATCH] nfsd: put dl_stid if fail to queue dl_recall

[Li Lingfeng <lilingfeng3@huawei.com>]

Before calling nfsd4_run_cb to queue dl_recall to the callback_wq, we
increment the reference count of dl_stid.
We expect that after the corresponding work_struct is processed, the
reference count of dl_stid will be decremented through the callback
function nfsd4_cb_recall_release.
However, if the call to nfsd4_run_cb fails, the incremented reference
count of dl_stid will not be decremented correspondingly, leading to the
following nfs4_stid leak:
unreferenced object 0xffff88812067b578 (size 344):
  comm "nfsd", pid 2761, jiffies 4295044002 (age 5541.241s)
  hex dump (first 32 bytes):
    01 00 00 00 6b 6b 6b 6b b8 02 c0 e2 81 88 ff ff  ....kkkk........
    00 6b 6b 6b 6b 6b 6b 6b 00 00 00 00 ad 4e ad de  .kkkkkkk.....N..
  backtrace:
    kmem_cache_alloc+0x4b9/0x700
    nfsd4_process_open1+0x34/0x300
    nfsd4_open+0x2d1/0x9d0
    nfsd4_proc_compound+0x7a2/0xe30
    nfsd_dispatch+0x241/0x3e0
    svc_process_common+0x5d3/0xcc0
    svc_process+0x2a3/0x320
    nfsd+0x180/0x2e0
    kthread+0x199/0x1d0
    ret_from_fork+0x30/0x50
    ret_from_fork_asm+0x1b/0x30
unreferenced object 0xffff8881499f4d28 (size 368):
  comm "nfsd", pid 2761, jiffies 4295044005 (age 5541.239s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 30 4d 9f 49 81 88 ff ff  ........0M.I....
    30 4d 9f 49 81 88 ff ff 20 00 00 00 01 00 00 00  0M.I.... .......
  backtrace:
    kmem_cache_alloc+0x4b9/0x700
    nfs4_alloc_stid+0x29/0x210
    alloc_init_deleg+0x92/0x2e0
    nfs4_set_delegation+0x284/0xc00
    nfs4_open_delegation+0x216/0x3f0
    nfsd4_process_open2+0x2b3/0xee0
    nfsd4_open+0x770/0x9d0
    nfsd4_proc_compound+0x7a2/0xe30
    nfsd_dispatch+0x241/0x3e0
    svc_process_common+0x5d3/0xcc0
    svc_process+0x2a3/0x320
    nfsd+0x180/0x2e0
    kthread+0x199/0x1d0
    ret_from_fork+0x30/0x50
    ret_from_fork_asm+0x1b/0x30
Fix it by checking the result of nfsd4_run_cb and call nfs4_put_stid if
fail to queue dl_recall.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
---
 fs/nfsd/nfs4state.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 153eeea2c7c9..0ccb87be47b7 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5414,6 +5414,7 @@ static const struct nfsd4_callback_ops nfsd4_cb_recall_ops = {
 
 static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
 {
+	bool queued;
 	/*
 	 * We're assuming the state code never drops its reference
 	 * without first removing the lease.  Since we're in this lease
@@ -5422,7 +5423,10 @@ static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
 	 * we know it's safe to take a reference.
 	 */
 	refcount_inc(&dp->dl_stid.sc_count);
-	WARN_ON_ONCE(!nfsd4_run_cb(&dp->dl_recall));
+	queued = nfsd4_run_cb(&dp->dl_recall);
+	WARN_ON_ONCE(!queued);
+	if (!queued)
+		nfs4_put_stid(&dp->dl_stid);
 }
 
 /* Called from break_lease() with flc_lock held. */
-- 
2.31.1