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authorEric Dumazet2022-06-22 15:02:20 +0000
committerJakub Kicinski2022-06-23 20:56:23 -0700
commit1228b34c8d0ecf6de18c4c95d22f60cc8607c50a (patch)
tree927562a5bd909ca11e403eadab6a53eeedaec36d /net
parentad887a507d7386de09a532c5d303ed659eba2cfb (diff)
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>
Diffstat (limited to 'net')
-rw-r--r--net/socket.c16
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;