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netdevsim: psp: serialize calls to nsim_psp_uninit()

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The debugfs write handler, nsim_psp_rereg_write(), can race against
nsim_destroy() and against itself, causing nsim_psp_uninit() to run
more than once concurrently. Two complementary changes serialize all
callers:

1. Delete the psp_rereg debugfs file from nsim_psp_uninit() before
   doing the actual teardown. debugfs_remove() drains any in-flight
   writers and prevents new ones from starting.

2. Add a mutex around the body of nsim_psp_rereg_write() so that two
   concurrent userspace writers cannot both enter the teardown path
   at once.

The teardown work itself is moved into a new __nsim_psp_uninit() that
the rereg handler calls under the mutex, while the public
nsim_psp_uninit() wraps it with the debugfs_remove()/mutex_destroy()
pair so nsim_destroy() doesn't have to know about the psp internals.

Fixes: f857478d62 ("netdevsim: a basic test PSP implementation")
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260505-psd-rcu-v1-2-a8f69ec1ab96@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Daniel Zahka
2026-05-05 03:42:24 -07:00
committed by Jakub Kicinski
parent 7ce3f1beda
commit 24c96a4200
2 changed files with 16 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/netdevsim/netdevsim.h
View File

@@ -121,6 +121,8 @@ struct netdevsim {
u64_stats_t tx_bytes;
struct u64_stats_sync syncp;
struct psp_dev *dev;
struct dentry *rereg;
struct mutex rereg_lock;
u32 spi;
u32 assoc_cnt;
} psp;

17
drivers/net/netdevsim/psp.c
View File

@@ -209,13 +209,20 @@ static struct psp_dev_caps nsim_psp_caps = {
.assoc_drv_spc = sizeof(void *),
};
void nsim_psp_uninit(struct netdevsim *ns)
static void __nsim_psp_uninit(struct netdevsim *ns)
{
if (!IS_ERR(ns->psp.dev))
psp_dev_unregister(ns->psp.dev);
WARN_ON(ns->psp.assoc_cnt);
}
void nsim_psp_uninit(struct netdevsim *ns)
{
debugfs_remove(ns->psp.rereg);
mutex_destroy(&ns->psp.rereg_lock);
__nsim_psp_uninit(ns);
}
static ssize_t
nsim_psp_rereg_write(struct file *file, const char __user *data, size_t count,
loff_t *ppos)
@@ -223,11 +230,13 @@ nsim_psp_rereg_write(struct file *file, const char __user *data, size_t count,
struct netdevsim *ns = file->private_data;
int err;
nsim_psp_uninit(ns);
mutex_lock(&ns->psp.rereg_lock);
__nsim_psp_uninit(ns);
ns->psp.dev = psp_dev_create(ns->netdev, &nsim_psp_ops,
&nsim_psp_caps, ns);
err = PTR_ERR_OR_ZERO(ns->psp.dev);
mutex_unlock(&ns->psp.rereg_lock);
return err ?: count;
}
@@ -249,6 +258,8 @@ int nsim_psp_init(struct netdevsim *ns)
if (err)
return err;
debugfs_create_file("psp_rereg", 0200, ddir, ns, &nsim_psp_rereg_fops);
mutex_init(&ns->psp.rereg_lock);
ns->psp.rereg = debugfs_create_file("psp_rereg", 0200, ddir, ns,
&nsim_psp_rereg_fops);
return 0;
}