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af_unix: introduce and use scm_replace_pid() helper 

Existing logic in __scm_send() related to filling an struct scm_cookie
with a proper struct pid reference is already pretty tricky. Let's
simplify it a bit by introducing a new helper. This helper will be
extended in one of the next patches.

Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-4-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Alexander Mikhalitsyn 2025-07-04 00:23:07 +02:00 committed by Christian Brauner
parent ee47976264
commit 30580dc96a
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1 changed files with 19 additions and 3 deletions
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22
net/core/scm.c
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@ -145,6 +145,16 @@ void __scm_destroy(struct scm_cookie *scm)
} }
EXPORT_SYMBOL(__scm_destroy); EXPORT_SYMBOL(__scm_destroy);
static inline int scm_replace_pid(struct scm_cookie *scm, struct pid *pid)
{
/* drop all previous references */
scm_destroy_cred(scm);
scm->pid = pid;
scm->creds.pid = pid_vnr(pid);
return 0;
}
int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
{ {
const struct proto_ops *ops = READ_ONCE(sock->ops); const struct proto_ops *ops = READ_ONCE(sock->ops);
@ -189,15 +199,21 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
if (err) if (err)
goto error; goto error;
p->creds.pid = creds.pid;
if (!p->pid || pid_vnr(p->pid) != creds.pid) { if (!p->pid || pid_vnr(p->pid) != creds.pid) {
struct pid *pid; struct pid *pid;
err = -ESRCH; err = -ESRCH;
pid = find_get_pid(creds.pid); pid = find_get_pid(creds.pid);
if (!pid) if (!pid)
goto error; goto error;
put_pid(p->pid);
p->pid = pid; /* pass a struct pid reference from
* find_get_pid() to scm_replace_pid().
*/
err = scm_replace_pid(p, pid);
if (err) {
put_pid(pid);
goto error;
}
} }
err = -EINVAL; err = -EINVAL;