linux-kernel - [PATCH v2 2/2] fs/fs_parse: Fix 3 issues for validate_constant

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Message-Id: <20250411-fix_fs-v2-2-5d3395c102e4@quicinc.com>
Date: Fri, 11 Apr 2025 23:31:41 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
 David Howells <dhowells@...hat.com>, Jonathan Corbet <corbet@....net>
Cc: Zijun Hu <zijun_hu@...oud.com>, linux-fsdevel@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
 Zijun Hu <quic_zijuhu@...cinc.com>
Subject: [PATCH v2 2/2] fs/fs_parse: Fix 3 issues for
 validate_constant_table()

From: Zijun Hu <quic_zijuhu@...cinc.com>

Constant table array array[] which must end with a empty entry and fix
below issues for validate_constant_table(array, ARRAY_SIZE(array), ...):

- Always return wrong value for good constant table array which ends
  with a empty entry.

- Imprecise error message for missorted case.

- Potential NULL pointer dereference since the last pr_err() may use
  'tbl[i].name' NULL pointer to print the last constant entry's name.

Fortunately, the function has no caller currently.
Fix these issues mentioned above.

Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
---
 fs/fs_parser.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index e635a81e17d965df78ffef27f6885cd70996c6dd..ef7876340a917876bc40df9cdde9232204125a75 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -399,6 +399,9 @@ bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 	}
 
 	for (i = 0; i < tbl_size; i++) {
+		if (!tbl[i].name && (i + 1 == tbl_size))
+			break;
+
 		if (!tbl[i].name) {
 			pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
 			good = false;
@@ -411,13 +414,13 @@ bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 				good = false;
 			}
 			if (c > 0) {
-				pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
+				pr_err("VALIDATE C-TBL[%zu]: Missorted %s>%s\n",
 				       i, tbl[i-1].name, tbl[i].name);
 				good = false;
 			}
 		}
 
-		if (tbl[i].value != special &&
+		if (tbl[i].name && tbl[i].value != special &&
 		    (tbl[i].value < low || tbl[i].value > high)) {
 			pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
 			       i, tbl[i].name, tbl[i].value, low, high);

-- 
2.34.1