linux-kernel - [PATCH 5.18 184/339] NFSD: Fix potential use-after-free in nfsd_file

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Message-Id: <20220613094932.258210982@linuxfoundation.org>
Date:   Mon, 13 Jun 2022 12:10:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Trond Myklebust <trondmy@...merspace.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 184/339] NFSD: Fix potential use-after-free in nfsd_file_put()

From: Chuck Lever <chuck.lever@...cle.com>

[ Upstream commit b6c71c66b0ad8f2b59d9bc08c7a5079b110bec01 ]

nfsd_file_put_noref() can free @nf, so don't dereference @nf
immediately upon return from nfsd_file_put_noref().

Suggested-by: Trond Myklebust <trondmy@...merspace.com>
Fixes: 999397926ab3 ("nfsd: Clean up nfsd_file_put()")
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/nfsd/filecache.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 2c1b027774d4..0326bdec5de7 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -306,11 +306,12 @@ nfsd_file_put(struct nfsd_file *nf)
 	if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0) {
 		nfsd_file_flush(nf);
 		nfsd_file_put_noref(nf);
-	} else {
+	} else if (nf->nf_file) {
 		nfsd_file_put_noref(nf);
-		if (nf->nf_file)
-			nfsd_file_schedule_laundrette();
-	}
+		nfsd_file_schedule_laundrette();
+	} else
+		nfsd_file_put_noref(nf);
+
 	if (atomic_long_read(&nfsd_filecache_count) >= NFSD_FILE_LRU_LIMIT)
 		nfsd_file_gc();
 }
-- 
2.35.1