From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Michael Tokarev Date: Wed, 1 Sep 2021 16:16:24 +0300 Subject: [PATCH] qemu-sockets: fix unix socket path copy (again) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commit 4cfd970ec188558daa6214f26203fe553fb1e01f added an assert which ensures the path within an address of a unix socket returned from the kernel is at least one byte and does not exceed sun_path buffer. Both of this constraints are wrong: A unix socket can be unnamed, in this case the path is completely empty (not even \0) And some implementations (notable linux) can add extra trailing byte (\0) _after_ the sun_path buffer if we passed buffer larger than it (and we do). So remove the assertion (since it causes real-life breakage) but at the same time fix the usage of sun_path. Namely, we should not access sun_path[0] if kernel did not return it at all (this is the case for unnamed sockets), and use the returned salen when copyig actual path as an upper constraint for the amount of bytes to copy - this will ensure we wont exceed the information provided by the kernel, regardless whenever there is a trailing \0 or not. This also helps with unnamed sockets. Note the case of abstract socket, the sun_path is actually a blob and can contain \0 characters, - it should not be passed to g_strndup and the like, it should be accessed by memcpy-like functions. Fixes: 4cfd970ec188558daa6214f26203fe553fb1e01f Fixes: http://bugs.debian.org/993145 Signed-off-by: Michael Tokarev Reviewed-by: Daniel P. Berrangé Reviewed-by: Marc-André Lureau CC: qemu-stable@nongnu.org --- util/qemu-sockets.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index f2f3676d1f..c5043999e9 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -1345,25 +1345,22 @@ socket_sockaddr_to_address_unix(struct sockaddr_storage *sa, SocketAddress *addr; struct sockaddr_un *su = (struct sockaddr_un *)sa; - assert(salen >= sizeof(su->sun_family) + 1 && - salen <= sizeof(struct sockaddr_un)); - addr = g_new0(SocketAddress, 1); addr->type = SOCKET_ADDRESS_TYPE_UNIX; + salen -= offsetof(struct sockaddr_un, sun_path); #ifdef CONFIG_LINUX - if (!su->sun_path[0]) { + if (salen > 0 && !su->sun_path[0]) { /* Linux abstract socket */ - addr->u.q_unix.path = g_strndup(su->sun_path + 1, - salen - sizeof(su->sun_family) - 1); + addr->u.q_unix.path = g_strndup(su->sun_path + 1, salen - 1); addr->u.q_unix.has_abstract = true; addr->u.q_unix.abstract = true; addr->u.q_unix.has_tight = true; - addr->u.q_unix.tight = salen < sizeof(*su); + addr->u.q_unix.tight = salen < sizeof(su->sun_path); return addr; } #endif - addr->u.q_unix.path = g_strndup(su->sun_path, sizeof(su->sun_path)); + addr->u.q_unix.path = g_strndup(su->sun_path, salen); return addr; } #endif /* WIN32 */