linux-kernel - [PATCH v1 06/14] mm/mshare: Check for mounted filesystem

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Date:   Mon, 11 Apr 2022 10:05:50 -0600
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     akpm@...ux-foundation.org, willy@...radead.org
Cc:     Khalid Aziz <khalid.aziz@...cle.com>, aneesh.kumar@...ux.ibm.com,
        arnd@...db.de, 21cnbao@...il.com, corbet@....net,
        dave.hansen@...ux.intel.com, david@...hat.com,
        ebiederm@...ssion.com, hagen@...u.net, jack@...e.cz,
        keescook@...omium.org, kirill@...temov.name, kucharsk@...il.com,
        linkinjeon@...nel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        longpeng2@...wei.com, luto@...nel.org, markhemm@...glemail.com,
        pcc@...gle.com, rppt@...nel.org, sieberf@...zon.com,
        sjpark@...zon.de, surenb@...gle.com, tst@...oebel-theuer.de,
        yzaikin@...gle.com
Subject: [PATCH v1 06/14] mm/mshare: Check for mounted filesystem

Check if msharefs is mounted before performing any msharefs
operations to avoid inadvertent NULL pointer dereferences.

Signed-off-by: Khalid Aziz <khalid.aziz@...cle.com>
---
 mm/mshare.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/mshare.c b/mm/mshare.c
index 85ccb7f02f33..cd2f7ad24d9d 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -176,6 +176,13 @@ SYSCALL_DEFINE5(mshare, const char __user *, name, unsigned long, addr,
 	struct qstr namestr;
 	int err = PTR_ERR(fname);
 
+	/*
+	 * Is msharefs mounted? TODO: If not mounted, return error
+	 * or automount?
+	 */
+	if (msharefs_sb == NULL)
+		return -ENOENT;
+
 	/*
 	 * Address range being shared must be aligned to pgdir
 	 * boundary and its size must be a multiple of pgdir size
@@ -260,6 +267,9 @@ SYSCALL_DEFINE1(mshare_unlink, const char *, name)
 	struct mshare_data *info;
 	struct qstr namestr;
 
+	if (msharefs_sb == NULL)
+		return -ENOENT;
+
 	if (IS_ERR(fname))
 		goto err_out;
 
-- 
2.32.0