Re: [PATCH] net: avoid double iput when sock_alloc_file fails

On May 3, 2023, at 7:31 AM, Dan Carpenter [off-list ref] wrote:

I changed the CC list from netdev to linux-nfs.

On Tue, Mar 07, 2023 at 02:37:07PM -0300, Thadeu Lima de Souza Cascardo wrote:

quoted

When sock_alloc_file fails to allocate a file, it will call sock_release.
__sys_socket_file should then not call sock_release again, otherwise there
will be a double free.

It's just a one liner to make Smatch warn about these sorts of user
after free bugs.

{ "sock_release", PARAM_FREED, 0, "$" },

Smatch found a related bug in nfs.

net/sunrpc/svcsock.c:938 svc_tcp_accept() warn: 'newsock' was already freed.
net/sunrpc/svcsock.c:1633 svc_create_socket() warn: 'sock' was already freed.
net/sunrpc/svcsock.c:1555 svc_addsock() error: dereferencing freed memory 'so'
net/sunrpc/svcsock.c:1633 svc_create_socket() warn: passing freed memory 'sock'
net/sunrpc/svcsock.c:938 svc_tcp_accept() warn: passing freed memory 'newsock'

I guess the svc_setup_socket() function should free sock on every error
path?  It seems kind of gnarly.

I'm looking at current upstream, and I don't see svc_setup_socket()
releasing @sock on any return path. What am I missing?

Does your tree have "SUNRPC: Ensure server-side sockets have a sock->file" ?


--
Chuck Lever