[PATCH net-next 1/2] netconsole: avoid printing partially updated target attributes
flat view
COOLING4d
SUPERSEDED
From: Gustavo Luiz Duarte <hidden>
Date: 2026-10-06 18:59:08
Also in:
lkml
Subsystem:
netconsole, networking drivers, the rest · Maintainers:
Breno Leitao, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Revision v1 of 2 in this series.
Revisions (2)
- v1 current
- v2 [diff vs current]
The configfs store callbacks all serialize on dynamic_netconsole_mutex but not on the read side, so reading an attribute while it is being written returns a partially updated value. Hold dynamic_netconsole_mutex on *_show() callbacks to avoid racing with writers. The dev_name_show() callback can also race with netconsole_netdev_event() writing to np.dev_name due to NETDEV_CHANGENAME. So it needs to hold RTNL in addition to dynamic_netconsole_mutex. Reported-by: Sashiko <netdev-bot+sashiko@kernel.org> Closes: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260814-netcons_ipv6-v3-7-bc0915e8c75f@gmail.com Closes: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260928-netcons-fixes-v1-0-bb5ffe5e698a%40gmail.com Signed-off-by: Gustavo Luiz Duarte <redacted> --- drivers/net/netconsole.c | 62 +++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 51 insertions(+), 11 deletions(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 267254f046de..188beacb308d 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c@@ -859,7 +859,19 @@ static ssize_t release_show(struct config_item *item, char *buf) static ssize_t dev_name_show(struct config_item *item, char *buf) { - return sysfs_emit(buf, "%s\n", to_target(item)->np.dev_name); + struct netconsole_target *nt = to_target(item); + int ret; + + dynamic_netconsole_mutex_lock(); + /* Hold RTNL to prevent racing against netconsole_netdev_event() + * changing np.dev_name. + */ + rtnl_lock(); + ret = sysfs_emit(buf, "%s\n", nt->np.dev_name); + rtnl_unlock(); + dynamic_netconsole_mutex_unlock(); + + return ret; } static ssize_t local_port_show(struct config_item *item, char *buf)
@@ -875,25 +887,39 @@ static ssize_t remote_port_show(struct config_item *item, char *buf) static ssize_t local_ip_show(struct config_item *item, char *buf) { struct netconsole_target *nt = to_target(item); + int ret; + + dynamic_netconsole_mutex_lock(); if (nt->local_ip.family == AF_UNSPEC) - return sysfs_emit(buf, "\n"); - if (nt->local_ip.family == AF_INET6) - return sysfs_emit(buf, "%pI6c\n", &nt->local_ip.in6); + ret = sysfs_emit(buf, "\n"); + else if (nt->local_ip.family == AF_INET6) + ret = sysfs_emit(buf, "%pI6c\n", &nt->local_ip.in6); else - return sysfs_emit(buf, "%pI4\n", &nt->local_ip.ip); + ret = sysfs_emit(buf, "%pI4\n", &nt->local_ip.ip); + + dynamic_netconsole_mutex_unlock(); + + return ret; } static ssize_t remote_ip_show(struct config_item *item, char *buf) { struct netconsole_target *nt = to_target(item); + int ret; + + dynamic_netconsole_mutex_lock(); if (nt->remote_ip.family == AF_UNSPEC) - return sysfs_emit(buf, "\n"); - if (nt->remote_ip.family == AF_INET6) - return sysfs_emit(buf, "%pI6c\n", &nt->remote_ip.in6); + ret = sysfs_emit(buf, "\n"); + else if (nt->remote_ip.family == AF_INET6) + ret = sysfs_emit(buf, "%pI6c\n", &nt->remote_ip.in6); else - return sysfs_emit(buf, "%pI4\n", &nt->remote_ip.ip); + ret = sysfs_emit(buf, "%pI4\n", &nt->remote_ip.ip); + + dynamic_netconsole_mutex_unlock(); + + return ret; } static ssize_t local_mac_show(struct config_item *item, char *buf)
@@ -906,7 +932,14 @@ static ssize_t local_mac_show(struct config_item *item, char *buf) static ssize_t remote_mac_show(struct config_item *item, char *buf) { - return sysfs_emit(buf, "%pM\n", to_target(item)->remote_mac); + struct netconsole_target *nt = to_target(item); + int ret; + + dynamic_netconsole_mutex_lock(); + ret = sysfs_emit(buf, "%pM\n", nt->remote_mac); + dynamic_netconsole_mutex_unlock(); + + return ret; } static ssize_t transmit_errors_show(struct config_item *item, char *buf)
@@ -1342,7 +1375,14 @@ static struct netconsole_target *userdata_to_target(struct userdata *ud) static ssize_t userdatum_value_show(struct config_item *item, char *buf) { - return sysfs_emit(buf, "%s\n", &(to_userdatum(item)->value[0])); + struct userdatum *udm = to_userdatum(item); + int ret; + + dynamic_netconsole_mutex_lock(); + ret = sysfs_emit(buf, "%s\n", udm->value); + dynamic_netconsole_mutex_unlock(); + + return ret; } /* Navigate configfs and calculate the lentgh of the formatted string
--
2.55.0