On Tue, Aug 31, 2021 at 10:26 PM Michael Tokarev <
mjt@tls.msk.ru> wrote:
We test whenever the path of unix-domain socket
address is non-empty and strictly-less than
the length of the path buffer. Both these
conditions are wrong: the socket can be unnamed,
with empty path, or socket can have pathname
null-terminated _after_ the sun_path buffer,
since we provided more room when asking kernel.
So on one side, allow empty, unnamed sockets
(and adjust the test for abstract socket too -
only do that if the socket is not unnamed),
and on another side, allow path length to be
up to our own maximum, - we have up to size
of sockaddr_storage there.
While at it, fix the duplication of regular
pathname socket to not require trailing \0
(since it can be missing for unnamed sockets).
Fixes: 4cfd970ec188558daa6214f26203fe553fb1e01f (first in 6.1.0)
Fixes: http://bugs.debian.org/993145
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: qemu-stable@nongnu.org
--
Two questions.
1. Why do we store the name of the socket to start with?
2. The code in the abstract socket case should not use
g_strndup but g_memdup instead, since the whole thing
is a blob of the given length, not a \0-terminated string.
---
util/qemu-sockets.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index f2f3676d1f..7c83d81792 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -1345,13 +1345,20 @@ 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));
+ /* there's a corner case when trailing \0 does not fit into
+ * sockaddr_un. Compare length with sizeof(sockaddr_storage),
+ * not with sizeof(sockaddr_un), since this is what we actually
+ * provide, to ensure we had no truncation and a room for
+ * the trailing \0 which we add below.
+ * When salen == sizeof(sun_family) it is unnamed socket,
+ * and when first byte of sun_path is \0, it is abstract. */
+ assert(salen >= sizeof(su->sun_family) &&
+ salen <= sizeof(struct sockaddr_storage));
Seems right to me, however there are some notes in libc bits/socket.h
/* Structure large enough to hold any socket address (with the historical
exception of AF_UNIX). */
And also this
I must say I feel confused by those comments :) Is it large enough or not??
addr = g_new0(SocketAddress, 1);
addr->type = SOCKET_ADDRESS_TYPE_UNIX;
#ifdef CONFIG_LINUX
- if (!su->sun_path[0]) {
+ if (salen > sizeof(su->sun_family) && !su->sun_path[0]) {
/* Linux abstract socket */
addr->u.q_unix.path = g_strndup(su->sun_path + 1,
salen - sizeof(su->sun_family) - 1);
@@ -1363,7 +1370,7 @@ socket_sockaddr_to_address_unix(struct sockaddr_storage *sa,
}
#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 - sizeof(su->sun_family));
looks good to me otherwise
return addr;
}
#endif /* WIN32 */
--
2.30.2