Re: [PATCH v2 1/1] af_unix: Fix memory leak in unix_dgram_sendmsg()

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Adrian Huang <adrianhuang0701@gmail.com>
Date: Tue, 25 Feb 2025 10:14:57 +0800
> From: Adrian Huang <ahuang12@lenovo.com>
> 
> After running the 'sendmsg02' program of Linux Test Project (LTP),
> kmemleak reports the following memory leak:
> 
>   # cat /sys/kernel/debug/kmemleak
>   unreferenced object 0xffff888243866800 (size 2048):
>     comm "sendmsg02", pid 67, jiffies 4294903166
>     hex dump (first 32 bytes):
>       00 00 00 00 00 00 00 00 5e 00 00 00 00 00 00 00  ........^.......
>       01 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
>     backtrace (crc 7e96a3f2):
>       kmemleak_alloc+0x56/0x90
>       kmem_cache_alloc_noprof+0x209/0x450
>       sk_prot_alloc.constprop.0+0x60/0x160
>       sk_alloc+0x32/0xc0
>       unix_create1+0x67/0x2b0
>       unix_create+0x47/0xa0
>       __sock_create+0x12e/0x200
>       __sys_socket+0x6d/0x100
>       __x64_sys_socket+0x1b/0x30
>       x64_sys_call+0x7e1/0x2140
>       do_syscall_64+0x54/0x110
>       entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> Commit 689c398885cc ("af_unix: Defer sock_put() to clean up path in
> unix_dgram_sendmsg().") defers sock_put() in the error handling path.
> However, it fails to account for the condition 'msg->msg_namelen != 0',
> resulting in a memory leak when the code jumps to the 'lookup' label.
> 
> Fix issue by calling sock_put() if 'msg->msg_namelen != 0' is met.
> 
> Fixes: 689c398885cc ("af_unix: Defer sock_put() to clean up path in unix_dgram_sendmsg().")
> Signed-off-by: Adrian Huang <ahuang12@lenovo.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Thanks!