From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Mon, 29 Mar 2021 20:46:05 +0000 (-0400)
Subject: NFS: Deal correctly with attribute generation counter overflow
X-Git-Tag: v5.11.22~190
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=419e9b1cac512f20e4527d1ddf29e39d88af0469;p=thirdparty%2Fkernel%2Fstable.git

NFS: Deal correctly with attribute generation counter overflow

[ Upstream commit 9fdbfad1777cb4638f489eeb62d85432010c0031 ]

We need to use unsigned long subtraction and then convert to signed in
order to deal correcly with C overflow rules.

Fixes: f5062003465c ("NFS: Set an attribute barrier on all updates")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 522aa10a1a3e7..fd073b1caf6c8 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1635,10 +1635,10 @@ EXPORT_SYMBOL_GPL(_nfs_display_fhandle);
  */
 static int nfs_inode_attrs_need_update(const struct inode *inode, const struct nfs_fattr *fattr)
 {
-	const struct nfs_inode *nfsi = NFS_I(inode);
+	unsigned long attr_gencount = NFS_I(inode)->attr_gencount;
 
-	return ((long)fattr->gencount - (long)nfsi->attr_gencount) > 0 ||
-		((long)nfsi->attr_gencount - (long)nfs_read_attr_generation_counter() > 0);
+	return (long)(fattr->gencount - attr_gencount) > 0 ||
+	       (long)(attr_gencount - nfs_read_attr_generation_counter()) > 0;
 }
 
 static int nfs_refresh_inode_locked(struct inode *inode, struct nfs_fattr *fattr)
@@ -2067,7 +2067,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 			nfsi->attrtimeo_timestamp = now;
 		}
 		/* Set the barrier to be more recent than this fattr */
-		if ((long)fattr->gencount - (long)nfsi->attr_gencount > 0)
+		if ((long)(fattr->gencount - nfsi->attr_gencount) > 0)
 			nfsi->attr_gencount = fattr->gencount;
 	}