diff options
Diffstat (limited to 'meta/recipes-devtools/qemu/qemu/CVE-2020-35517.patch')
| -rw-r--r-- | meta/recipes-devtools/qemu/qemu/CVE-2020-35517.patch | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2020-35517.patch b/meta/recipes-devtools/qemu/qemu/CVE-2020-35517.patch new file mode 100644 index 0000000000..f818eb3bf5 --- /dev/null +++ b/meta/recipes-devtools/qemu/qemu/CVE-2020-35517.patch @@ -0,0 +1,126 @@ +From ebf101955ce8f8d72fba103b5151115a4335de2c Mon Sep 17 00:00:00 2001 +From: Stefan Hajnoczi <stefanha@redhat.com> +Date: Tue, 6 Oct 2020 10:58:26 +0100 +Subject: [PATCH] virtiofsd: avoid /proc/self/fd tempdir + +In order to prevent /proc/self/fd escapes a temporary directory is +created where /proc/self/fd is bind-mounted. This doesn't work on +read-only file systems. + +Avoid the temporary directory by bind-mounting /proc/self/fd over /proc. +This does not affect other processes since we remounted / with MS_REC | +MS_SLAVE. /proc must exist and virtiofsd does not use it so it's safe to +do this. + +Path traversal can be tested with the following function: + + static void test_proc_fd_escape(struct lo_data *lo) + { + int fd; + int level = 0; + ino_t last_ino = 0; + + fd = lo->proc_self_fd; + for (;;) { + struct stat st; + + if (fstat(fd, &st) != 0) { + perror("fstat"); + return; + } + if (last_ino && st.st_ino == last_ino) { + fprintf(stderr, "inode number unchanged, stopping\n"); + return; + } + last_ino = st.st_ino; + + fprintf(stderr, "Level %d dev %lu ino %lu\n", level, + (unsigned long)st.st_dev, + (unsigned long)last_ino); + fd = openat(fd, "..", O_PATH | O_DIRECTORY | O_NOFOLLOW); + level++; + } + } + +Before and after this patch only Level 0 is displayed. Without +/proc/self/fd bind-mount protection it is possible to traverse parent +directories. + +Fixes: 397ae982f4df4 ("virtiofsd: jail lo->proc_self_fd") +Cc: Miklos Szeredi <mszeredi@redhat.com> +Cc: Jens Freimann <jfreimann@redhat.com> +Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> +Message-Id: <20201006095826.59813-1-stefanha@redhat.com> +Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> +Tested-by: Jens Freimann <jfreimann@redhat.com> +Reviewed-by: Jens Freimann <jfreimann@redhat.com> +Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> + + +Upstream-Status: Backport +[https://github.com/qemu/qemu/commit/ebf101955ce8f8d72fba103b5151115a4335de2c] +CVE: CVE-2020-35517 +Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com> + +--- + tools/virtiofsd/passthrough_ll.c | 34 +++++++++++--------------------- + 1 file changed, 11 insertions(+), 23 deletions(-) + +diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c +index 477e6ee0b53..ff53df44510 100644 +--- a/tools/virtiofsd/passthrough_ll.c ++++ b/tools/virtiofsd/passthrough_ll.c +@@ -2393,8 +2393,6 @@ static void setup_wait_parent_capabilities(void) + static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) + { + pid_t child; +- char template[] = "virtiofsd-XXXXXX"; +- char *tmpdir; + + /* + * Create a new pid namespace for *child* processes. We'll have to +@@ -2458,33 +2456,23 @@ static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) + exit(1); + } + +- tmpdir = mkdtemp(template); +- if (!tmpdir) { +- fuse_log(FUSE_LOG_ERR, "tmpdir(%s): %m\n", template); +- exit(1); +- } +- +- if (mount("/proc/self/fd", tmpdir, NULL, MS_BIND, NULL) < 0) { +- fuse_log(FUSE_LOG_ERR, "mount(/proc/self/fd, %s, MS_BIND): %m\n", +- tmpdir); ++ /* ++ * We only need /proc/self/fd. Prevent ".." from accessing parent ++ * directories of /proc/self/fd by bind-mounting it over /proc. Since / was ++ * previously remounted with MS_REC | MS_SLAVE this mount change only ++ * affects our process. ++ */ ++ if (mount("/proc/self/fd", "/proc", NULL, MS_BIND, NULL) < 0) { ++ fuse_log(FUSE_LOG_ERR, "mount(/proc/self/fd, MS_BIND): %m\n"); + exit(1); + } + +- /* Now we can get our /proc/self/fd directory file descriptor */ +- lo->proc_self_fd = open(tmpdir, O_PATH); ++ /* Get the /proc (actually /proc/self/fd, see above) file descriptor */ ++ lo->proc_self_fd = open("/proc", O_PATH); + if (lo->proc_self_fd == -1) { +- fuse_log(FUSE_LOG_ERR, "open(%s, O_PATH): %m\n", tmpdir); ++ fuse_log(FUSE_LOG_ERR, "open(/proc, O_PATH): %m\n"); + exit(1); + } +- +- if (umount2(tmpdir, MNT_DETACH) < 0) { +- fuse_log(FUSE_LOG_ERR, "umount2(%s, MNT_DETACH): %m\n", tmpdir); +- exit(1); +- } +- +- if (rmdir(tmpdir) < 0) { +- fuse_log(FUSE_LOG_ERR, "rmdir(%s): %m\n", tmpdir); +- } + } + + /* |