在 2025/2/13 20:34, Jeff Layton 写道:
On Thu, 2025-02-13 at 20:28 +0800, Li Lingfeng wrote:
在 2025/2/13 19:49, Jeff Layton 写道:
On Thu, 2025-02-13 at 15:25 +0800, Li Lingfeng wrote:
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@xxxxxxxxxx>
---
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. */
Have you actually seen the WARN_ON_ONCE() pop under normal usage, or
was the problem you reproduced done via fault injection?
Hi,
I add mdelay for cb_work before processing it and add msleep in
nfs_do_return_delegation to reproduce it.
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1188,6 +1188,8 @@ alloc_init_deleg(struct nfs4_client *clp, struct
nfs4_file *fp,
dp->dl_recalled = false;
nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
&nfsd4_cb_recall_ops, NFSPROC4_CLNT_CB_RECALL);
+ dp->dl_recall.cb_work.debug_flag = 0x1234;
+ printk("%s init work func %px\n", __func__,
dp->dl_recall.cb_work.func);
get_nfs4_file(fp);
dp->dl_stid.sc_file = fp;
return dp;
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2708,6 +2708,12 @@ static void process_scheduled_works(struct worker
*worker)
worker->pool->watchdog_ts = jiffies;
first = false;
}
+ if (work->debug_flag == 0x1234) {
+ printk("%s func %px\n", __func__, work->func);
+ printk("%s delay before clear pending...\n", __func__);
+ mdelay(10 * 1000);
+ printk("%s delay done\n", __func__);
+ }
process_one_work(worker, work);
}
}
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -263,6 +263,15 @@ static int nfs_do_return_delegation(struct inode
*inode, struct nfs_delegation *
const struct cred *cred;
int res = 0;
+ printk("sleep before deleg return...\n");
+ while (1) {
+ ifdebug(PROC)
+ msleep(10 * 1000);
+ else
+ break;
+ }
+ printk("sleep done\n");
+
if (!test_bit(NFS_DELEGATION_REVOKED, &delegation-flags)) {
spin_lock(&delegation->lock);
cred = get_cred(delegation->cred);
Unfortunately, this won't work. nfsd_break_one_deleg() is called from
the ->break_lease callback with the flc->flc_lock held, and
nfs4_put_stid can sleep in the sc_free callbacks.
Are you referring to nfs4_free_deleg? I didn't quite see where it might
sleep. Could you please explain it to me?
I stand corrected. nfs4_free_deleg() won't sleep, but
nfs4_free_lock_stateid() can. In this case, you know that this is a
deleg stateid, so this should actually be safe after all.
If you do this though, please add a comment to nfs4_free_deleg()
mentioning that it mustn't ever sleep, since it can be called from that
context.
Thank you for your advice, I will send v2 soon.
