From 5018a0c016495155ee598b7e0167b43d5d902414 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Sat, 14 Jul 2018 03:47:50 -0700 Subject: [PATCH] fusermount: refuse unknown options Blacklists are notoriously fragile; especially if the kernel wishes to add some security-critical mount option at a later date, all existing systems with older versions of fusermount installed will suddenly have a security problem. Additionally, if the kernel's option parsing became a tiny bit laxer, the blacklist could probably be bypassed. Whitelist known-harmless flags instead, even if it's slightly more inconvenient. --- util/fusermount.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/util/fusermount.c b/util/fusermount.c index 4e0f51a3..27924073 100644 --- a/util/fusermount.c +++ b/util/fusermount.c @@ -819,10 +819,16 @@ static int do_mount(const char *mnt, char **typep, mode_t rootmode, flags |= flag; else flags &= ~flag; - } else { + } else if (opt_eq(s, len, "default_permissions") || + opt_eq(s, len, "allow_other") || + begins_with(s, "max_read=") || + begins_with(s, "blksize=")) { memcpy(d, s, len); d += len; *d++ = ','; + } else { + fprintf(stderr, "%s: unknown option '%.*s'\n", progname, len, s); + exit(1); } } }