CBL-Mariner/SPECS/fuse/fuse-refuse-unknown-options...

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From 5018a0c016495155ee598b7e0167b43d5d902414 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
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);
}
}
}