[PATCH] copy_process(): fix a memleak in copy_process()

[Gaosheng Cui]

If CLONE_PIDFD is set in clone_flags, pidfile will hold the reference
count of pid by getpid(pid), In the error path bad_fork_put_pidfd, the
reference of pid needs to be released, otherwise there will be a
memleak issue, fix it.

unreferenced object 0xffff888164aed400 (size 224):
  comm "sh", pid 75274, jiffies 4295717290 (age 2955.536s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de  .............N..
    ff ff ff ff 00 00 00 00 ff ff ff ff ff ff ff ff  ................
  backtrace:
    [<00000000bcb9eebb>] kmem_cache_alloc+0x16a/0x7f0
    [<00000000340cf9ad>] alloc_pid+0xc5/0xce0
    [<000000002387362c>] copy_process+0x29ef/0x6c90
    [<00000000bf7d7efc>] kernel_clone+0xd9/0xc70
    [<0000000047b1a04f>] __do_sys_clone+0xe1/0x120
    [<0000000000f1aa25>] __x64_sys_clone+0xc3/0x150
    [<00000000250a19f1>] do_syscall_64+0x5c/0x90
    [<000000007e0ac417>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups")
Signed-off-by: Gaosheng Cui <cuigaosheng1@xxxxxxxxxx>
---
 kernel/fork.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/fork.c b/kernel/fork.c
index 08969f5aa38d..8706c06be8af 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2499,6 +2499,7 @@ static __latent_entropy struct task_struct *copy_process(
 	cgroup_cancel_fork(p, args);
 bad_fork_put_pidfd:
 	if (clone_flags & CLONE_PIDFD) {
+		put_pid(pid);
 		fput(pidfile);
 		put_unused_fd(pidfd);
 	}
-- 
2.25.1