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kobject: make uevent_seqnum atomic 

We will soon no longer acquire uevent_sock_mutex
for most kobject_uevent_net_broadcast() calls,
and also while calling uevent_net_broadcast().

Make uevent_seqnum an atomic64_t to get its own protection.

This fixes a race while reading /sys/kernel/uevent_seqnum.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christian Brauner <brauner@kernel.org>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20240214084829.684541-2-edumazet@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2024-02-14 08:48:28 +00:00 committed by Greg Kroah-Hartman
parent 5df9197edd
commit 2444a80c1c
3 changed files with 11 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/kobject.h
View File

@ -38,7 +38,7 @@ extern char uevent_helper[];
#endif
/* counter to tag the uevent, read only except for the kobject core */
extern u64 uevent_seqnum;
extern atomic64_t uevent_seqnum;
/*
* The actions here must match the index to the string array

2
kernel/ksysfs.c
View File

@ -39,7 +39,7 @@ static struct kobj_attribute _name##_attr = __ATTR_RW(_name)
static ssize_t uevent_seqnum_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%llu\n", (unsigned long long)uevent_seqnum);
return sysfs_emit(buf, "%llu\n", (u64)atomic64_read(&uevent_seqnum));
}
KERNEL_ATTR_RO(uevent_seqnum);

17
lib/kobject_uevent.c
View File

@ -30,7 +30,7 @@
#include <net/net_namespace.h>
u64 uevent_seqnum;
atomic64_t uevent_seqnum;
#ifdef CONFIG_UEVENT_HELPER
char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
#endif
@ -44,7 +44,7 @@ struct uevent_sock {
static LIST_HEAD(uevent_sock_list);
#endif
/* This lock protects uevent_seqnum and uevent_sock_list */
/* This lock protects uevent_sock_list */
static DEFINE_MUTEX(uevent_sock_mutex);
/* the strings here must match the enum in include/linux/kobject.h */
@ -583,13 +583,13 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
break;
}
mutex_lock(&uevent_sock_mutex);
/* we will send an event, so request a new sequence number */
retval = add_uevent_var(env, "SEQNUM=%llu", ++uevent_seqnum);
if (retval) {
mutex_unlock(&uevent_sock_mutex);
retval = add_uevent_var(env, "SEQNUM=%llu",
atomic64_inc_return(&uevent_seqnum));
if (retval)
goto exit;
}
mutex_lock(&uevent_sock_mutex);
retval = kobject_uevent_net_broadcast(kobj, env, action_string,
devpath);
mutex_unlock(&uevent_sock_mutex);
@ -688,7 +688,8 @@ static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
int ret;
/* bump and prepare sequence number */
ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu", ++uevent_seqnum);
ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu",
atomic64_inc_return(&uevent_seqnum));
if (ret < 0 || (size_t)ret >= sizeof(buf))
return -ENOMEM;
ret++;