[PATCH 4/4] mkfs: terminate getsubopt arrays properly

From: "Darrick J. Wong" <djwong@kernel.org>
To: sandeen@sandeen.net, djwong@kernel.org
Cc: linux-xfs@vger.kernel.org
Subject: [PATCH 4/4] mkfs: terminate getsubopt arrays properly
Date: Tue, 12 Jul 2022 18:09:59 -0700	[thread overview]
Message-ID: <165767459958.891854.15344618102582353193.stgit@magnolia> (raw)
In-Reply-To: <165767457703.891854.2108521135190969641.stgit@magnolia>

From: Darrick J. Wong <djwong@kernel.org>

Having not drank any (or maybe too much) coffee this morning, I typed:

$ mkfs.xfs -d agcount=3 -d nrext64=0
Segmentation fault

I traced this down to getsubopt walking off the end of the dopts.subopts
array.  The manpage says you're supposed to terminate the suboptions
string array with a NULL entry, but the structure definition uses
MAX_SUBOPTS/D_MAX_OPTS directly, which means there is no terminator.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 mkfs/xfs_mkfs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 61ac1a4a..9a58ff8b 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -141,7 +141,7 @@ enum {
 };
 
 /* Just define the max options array size manually right now */
-#define MAX_SUBOPTS	D_MAX_OPTS
+#define MAX_SUBOPTS	(D_MAX_OPTS + 1)
 
 #define SUBOPT_NEEDS_VAL	(-1LL)
 #define MAX_CONFLICTS	8

