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From:   Khalid Aziz <khalid.aziz@oracle.com>
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Subject: [PATCH v1 06/14] mm/mshare: Check for mounted filesystem
Date:   Mon, 11 Apr 2022 10:05:50 -0600
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Check if msharefs is mounted before performing any msharefs
operations to avoid inadvertent NULL pointer dereferences.

Signed-off-by: Khalid Aziz <khalid.aziz@oracle.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