2020-04-20 17:30:54

by Trond Myklebust

[permalink] [raw]
Subject: [PATCH] NFS/pnfs: Fix a credential use-after-free issue in pnfs_roc()

From: Trond Myklebust <[email protected]>

If the credential returned by pnfs_prepare_layoutreturn()
does not match the credential of the RPC call, then we do
end up calling pnfs_send_layoutreturn() with that credential,
so don't free it!

Fixes: 44ea8dfce021 ("NFS/pnfs: Reference the layout cred in pnfs_prepare_layoutreturn()")
Signed-off-by: Trond Myklebust <[email protected]>
---
fs/nfs/pnfs.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 3bf6899cba95..dd2e14f5875d 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1458,18 +1458,15 @@ bool pnfs_roc(struct inode *ino,
/* lo ref dropped in pnfs_roc_release() */
layoutreturn = pnfs_prepare_layoutreturn(lo, &stateid, &lc_cred, &iomode);
/* If the creds don't match, we can't compound the layoutreturn */
- if (!layoutreturn)
+ if (!layoutreturn || cred_fscmp(cred, lc_cred) != 0)
goto out_noroc;
- if (cred_fscmp(cred, lc_cred) != 0)
- goto out_noroc_put_cred;

roc = layoutreturn;
pnfs_init_layoutreturn_args(args, lo, &stateid, iomode);
res->lrs_present = 0;
layoutreturn = false;
-
-out_noroc_put_cred:
put_cred(lc_cred);
+
out_noroc:
spin_unlock(&ino->i_lock);
rcu_read_unlock();
--
2.25.3