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author | Eric Dumazet <edumazet@google.com> | 2022-06-22 18:02:20 +0300 |
---|---|---|
committer | Jakub Kicinski <kuba@kernel.org> | 2022-06-24 06:56:23 +0300 |
commit | 1228b34c8d0ecf6de18c4c95d22f60cc8607c50a (patch) | |
tree | 927562a5bd909ca11e403eadab6a53eeedaec36d | |
parent | ad887a507d7386de09a532c5d303ed659eba2cfb (diff) | |
download | linux-1228b34c8d0ecf6de18c4c95d22f60cc8607c50a.tar.xz |
net: clear msg_get_inq in __sys_recvfrom() and __copy_msghdr_from_user()
syzbot reported uninit-value in tcp_recvmsg() [1]
Issue here is that msg->msg_get_inq should have been cleared,
otherwise tcp_recvmsg() might read garbage and perform
more work than needed, or have undefined behavior.
Given CONFIG_INIT_STACK_ALL_ZERO=y is probably going to be
the default soon, I chose to change __sys_recvfrom() to clear
all fields but msghdr.addr which might be not NULL.
For __copy_msghdr_from_user(), I added an explicit clear
of kmsg->msg_get_inq.
[1]
BUG: KMSAN: uninit-value in tcp_recvmsg+0x6cf/0xb60 net/ipv4/tcp.c:2557
tcp_recvmsg+0x6cf/0xb60 net/ipv4/tcp.c:2557
inet_recvmsg+0x13a/0x5a0 net/ipv4/af_inet.c:850
sock_recvmsg_nosec net/socket.c:995 [inline]
sock_recvmsg net/socket.c:1013 [inline]
__sys_recvfrom+0x696/0x900 net/socket.c:2176
__do_sys_recvfrom net/socket.c:2194 [inline]
__se_sys_recvfrom net/socket.c:2190 [inline]
__x64_sys_recvfrom+0x122/0x1c0 net/socket.c:2190
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
Local variable msg created at:
__sys_recvfrom+0x81/0x900 net/socket.c:2154
__do_sys_recvfrom net/socket.c:2194 [inline]
__se_sys_recvfrom net/socket.c:2190 [inline]
__x64_sys_recvfrom+0x122/0x1c0 net/socket.c:2190
CPU: 0 PID: 3493 Comm: syz-executor170 Not tainted 5.19.0-rc3-syzkaller-30868-g4b28366af7d9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Fixes: f94fd25cb0aa ("tcp: pass back data left in socket after receive")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Tested-by: Alexander Potapenko<glider@google.com>
Link: https://lore.kernel.org/r/20220622150220.1091182-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-rw-r--r-- | net/socket.c | 16 |
1 files changed, 6 insertions, 10 deletions
diff --git a/net/socket.c b/net/socket.c index 2bc8773d9dc5..96300cdc0625 100644 --- a/net/socket.c +++ b/net/socket.c @@ -2149,10 +2149,13 @@ SYSCALL_DEFINE4(send, int, fd, void __user *, buff, size_t, len, int __sys_recvfrom(int fd, void __user *ubuf, size_t size, unsigned int flags, struct sockaddr __user *addr, int __user *addr_len) { + struct sockaddr_storage address; + struct msghdr msg = { + /* Save some cycles and don't copy the address if not needed */ + .msg_name = addr ? (struct sockaddr *)&address : NULL, + }; struct socket *sock; struct iovec iov; - struct msghdr msg; - struct sockaddr_storage address; int err, err2; int fput_needed; @@ -2163,14 +2166,6 @@ int __sys_recvfrom(int fd, void __user *ubuf, size_t size, unsigned int flags, if (!sock) goto out; - msg.msg_control = NULL; - msg.msg_controllen = 0; - /* Save some cycles and don't copy the address if not needed */ - msg.msg_name = addr ? (struct sockaddr *)&address : NULL; - /* We assume all kernel code knows the size of sockaddr_storage */ - msg.msg_namelen = 0; - msg.msg_iocb = NULL; - msg.msg_flags = 0; if (sock->file->f_flags & O_NONBLOCK) flags |= MSG_DONTWAIT; err = sock_recvmsg(sock, &msg, flags); @@ -2375,6 +2370,7 @@ int __copy_msghdr_from_user(struct msghdr *kmsg, return -EFAULT; kmsg->msg_control_is_user = true; + kmsg->msg_get_inq = 0; kmsg->msg_control_user = msg.msg_control; kmsg->msg_controllen = msg.msg_controllen; kmsg->msg_flags = msg.msg_flags; |