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Tue, 06 Oct 2026 11:59:06 -0700 (PDT) From: Gustavo Luiz Duarte Date: Tue, 06 Oct 2026 19:58:29 +0100 Subject: [PATCH net-next 1/2] netconsole: avoid printing partially updated target attributes Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261006-netcons-fixes-next-v1-1-231cd26f8c51@gmail.com> References: <20261006-netcons-fixes-next-v1-0-231cd26f8c51@gmail.com> In-Reply-To: <20261006-netcons-fixes-next-v1-0-231cd26f8c51@gmail.com> To: Breno Leitao , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Gustavo Luiz Duarte , Sashiko X-Mailer: b4 0.15.2 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 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 --- 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