[PATCH v2] namespace: Added pointer check in copy_mnt_ns()

[Denis Arefev]

Return value of a function 'next_mnt' is dereferenced at
namespace.c:3377 without checking for null,
but it is usually checked for this function

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Denis Arefev <arefev@xxxxxxxxx>
---
 fs/namespace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index cebaa3e81794..06472a110257 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3348,9 +3348,9 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 		}
 		p = next_mnt(p, old);
 		q = next_mnt(q, new);
-		if (!q)
+		if (!q || !p)
 			break;
-		while (p->mnt.mnt_root != q->mnt.mnt_root)
+		while (p && (p->mnt.mnt_root != q->mnt.mnt_root))
 			p = next_mnt(p, old);
 	}
 	namespace_unlock();
-- 
2.25.1