| From 28bdae3d113ef479c1660a581ef720cdc33bf466 Mon Sep 17 00:00:00 2001 |
| From: Jann Horn <jannh@google.com> |
| Date: Fri, 13 Jul 2018 15:15:36 -0700 |
| Subject: [PATCH] fusermount: don't feed "escaped commas" into mount options |
| |
| The old code permits the following behavior: |
| |
| $ _FUSE_COMMFD=10000 priv_strace -etrace=mount -s200 fusermount -o 'foobar=\,allow_other' mount |
| mount("/dev/fuse", ".", "fuse", MS_NOSUID|MS_NODEV, "foobar=\\,allow_other,fd=3,rootmode=40000,user_id=1000,group_id=1000") = -1 EINVAL (Invalid argument) |
| |
| However, backslashes do not have any special meaning for the kernel here. |
| |
| As it happens, you can't abuse this because there is no FUSE mount option |
| that takes a string value that can contain backslashes; but this is very |
| brittle. Don't interpret "escape characters" in places where they don't |
| work. |
| |
| CVE: CVE-2018-10906 |
| Upstream-Status: Backport [https://github.com/libfuse/libfuse/commit/28bdae3d113ef479c1660a581ef720cdc33bf466] |
| |
| Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com> |
| --- |
| util/fusermount.c | 5 ++++- |
| 1 file changed, 4 insertions(+), 1 deletion(-) |
| |
| diff --git a/util/fusermount.c b/util/fusermount.c |
| index 0e1d34d..143bd4a 100644 |
| --- a/util/fusermount.c |
| +++ b/util/fusermount.c |
| @@ -29,6 +29,7 @@ |
| #include <sys/socket.h> |
| #include <sys/utsname.h> |
| #include <sched.h> |
| +#include <stdbool.h> |
| |
| #define FUSE_COMMFD_ENV "_FUSE_COMMFD" |
| |
| @@ -754,8 +755,10 @@ static int do_mount(const char *mnt, char **typep, mode_t rootmode, |
| unsigned len; |
| const char *fsname_str = "fsname="; |
| const char *subtype_str = "subtype="; |
| + bool escape_ok = begins_with(s, fsname_str) || |
| + begins_with(s, subtype_str); |
| for (len = 0; s[len]; len++) { |
| - if (s[len] == '\\' && s[len + 1]) |
| + if (escape_ok && s[len] == '\\' && s[len + 1]) |
| len++; |
| else if (s[len] == ',') |
| break; |
| -- |
| 2.13.3 |
| |