linux-kernel - [PATCH] nfs: Fix memory leak of export

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Date:   Fri, 12 Jun 2020 15:45:49 -0700
From:   trix@...hat.com
To:     trond.myklebust@...merspace.com, anna.schumaker@...app.com
Cc:     linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] nfs: Fix memory leak of export_path

From: Tom Rix <trix@...hat.com>

The try_location function is called within a loop by nfs_follow_referral.
try_location calls nfs4_pathname_string to created the export_path.
nfs4_pathname_string allocates the memory. export_path is stored in the
nfs_fs_context/fs_context structure similarly as hostname and source.
But whereas the ctx hostname and source are freed before assignment,
export_path is not.  So if there are multiple loops, the new export_path
will overwrite the old without the old being freed.

So call kfree for export_path.

Signed-off-by: Tom Rix <trix@...hat.com>
---
 fs/nfs/nfs4namespace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nfs/nfs4namespace.c b/fs/nfs/nfs4namespace.c
index a3ab6e219061..873342308dc0 100644
--- a/fs/nfs/nfs4namespace.c
+++ b/fs/nfs/nfs4namespace.c
@@ -308,6 +308,7 @@ static int try_location(struct fs_context *fc,
 	if (IS_ERR(export_path))
 		return PTR_ERR(export_path);

+	kfree(ctx->nfs_server.export_path);
 	ctx->nfs_server.export_path = export_path;

 	source = kmalloc(len + 1 + ctx->nfs_server.export_path_len + 1,
-- 
2.18.1