From a24221dca1868101c9b4b5adde4a6a5b1a3a64a7 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 24 Jun 2015 12:10:23 -0400 Subject: [PATCH] nfs: fix potential credential leak in ff_layout_update_mirror_cred If we have two tasks racing to update a mirror's credentials, then they can end up leaking one (or more) sets of credentials. The first task will set mirror->cred and then the second task will just overwrite it. Use a cmpxchg to ensure that the creds are only set once. If we get to the point where we would set mirror->cred and find that they're already set, then we just release the creds that were just found. Signed-off-by: Jeff Layton Cc: stable@vger.kernel.org # 4.0+ Signed-off-by: Trond Myklebust --- fs/nfs/flexfilelayout/flexfilelayoutdev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c index 77a2d026aa12..c19b9a88f748 100644 --- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c +++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c @@ -324,7 +324,8 @@ static int ff_layout_update_mirror_cred(struct nfs4_ff_layout_mirror *mirror, __func__, PTR_ERR(cred)); return PTR_ERR(cred); } else { - mirror->cred = cred; + if (cmpxchg(&mirror->cred, NULL, cred)) + put_rpccred(cred); } } return 0; -- 2.20.1