linux-kernel - [RFC PATCH 2/4] vfs: Make fs_parse() handle fs_param_is

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Date:   Tue, 19 Mar 2019 16:23:38 +0000
From:   David Howells <dhowells@...hat.com>
To:     miklos@...redi.hu, viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        dhowells@...hat.com, anprice@...hat.com
Subject: [RFC PATCH 2/4] vfs: Make fs_parse() handle fs_param_is_fd-type
 params better

Make fs_parse() handle fs_param_is_fd-type parameters that are passed a
string by converting it to an integer (in addition to handling direct fd
specification).

Also range check the integer.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/fs_parser.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index be86703ec371..bd59e1725c50 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -208,9 +208,20 @@ int fs_parse(struct fs_context *fc,
 		goto okay;
 
 	case fs_param_is_fd: {
-		if (param->type != fs_value_is_file)
+		switch (param->type) {
+		case fs_value_is_string:
+			ret = kstrtouint(param->string, 0, &result->uint_32);
+			break;
+		case fs_value_is_file:
+			result->uint_32 = param->dirfd;
+			ret = 0;
+		default:
 			goto bad_value;
-		goto okay;
+		}
+
+		if (result->uint_32 > INT_MAX)
+			goto bad_value;
+		goto maybe_okay;
 	}
 
 	case fs_param_is_blockdev: