From: Breno Leitao Date: Mon, 27 Apr 2026 14:30:35 +0000 (-0700) Subject: netconsole: return count instead of strnlen(buf, count) from store callbacks X-Git-Tag: v7.1-rc2~22^2~13^2~3 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d62c6f2df5c0e1390b9a1f45b1b52689e3f234f0;p=thirdparty%2Fkernel%2Flinux.git netconsole: return count instead of strnlen(buf, count) from store callbacks Several configfs store callbacks in netconsole end with: ret = strnlen(buf, count); This under-reports the number of bytes consumed when the input contains an embedded NUL within count, telling the VFS that fewer bytes were written than userspace actually handed in. A conformant partial-write loop would then retry the trailing bytes against a callback that has already accepted them. Every other configfs driver in the tree returns count directly from its store callbacks once parsing has succeeded, including drivers/nvme/target/configfs.c, drivers/gpio/gpio-sim.c, drivers/most/configfs.c, drivers/block/null_blk/main.c, drivers/pci/endpoint/pci-ep-cfs.c, and the rest of the configfs users. netconsole was the outlier (along with drivers/infiniband/core/cma_configfs.c, which has the same latent issue). Align netconsole with the rest of the configfs ecosystem: return count once the parser/validator has accepted the input. The numeric and boolean parsers (kstrtobool, kstrtou16, mac_pton, netpoll_parse_ip_addr) have already validated the meaningful prefix; any trailing bytes are padding and should simply be reported as consumed. Fixes: 0bcc1816188e ("[NET] netconsole: Support dynamic reconfiguration using configfs") Reviewed-by: Simon Horman Signed-off-by: Breno Leitao Link: https://patch.msgid.link/20260427-netconsole_ai_fixes-v2-1-59965f29d9cc@debian.org Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 205384dab89a..76d7fbf9e188 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -752,7 +752,7 @@ static ssize_t enabled_store(struct config_item *item, unregister_netcons_consoles(); } - ret = strnlen(buf, count); + ret = count; /* Deferred cleanup */ netconsole_process_cleanups(); out_unlock: @@ -781,7 +781,7 @@ static ssize_t release_store(struct config_item *item, const char *buf, nt->release = release; - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -807,7 +807,7 @@ static ssize_t extended_store(struct config_item *item, const char *buf, goto out_unlock; nt->extended = extended; - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -830,7 +830,7 @@ static ssize_t dev_name_store(struct config_item *item, const char *buf, trim_newline(nt->np.dev_name, IFNAMSIZ); dynamic_netconsole_mutex_unlock(); - return strnlen(buf, count); + return count; } static ssize_t local_port_store(struct config_item *item, const char *buf, @@ -849,7 +849,7 @@ static ssize_t local_port_store(struct config_item *item, const char *buf, ret = kstrtou16(buf, 10, &nt->np.local_port); if (ret < 0) goto out_unlock; - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -871,7 +871,7 @@ static ssize_t remote_port_store(struct config_item *item, ret = kstrtou16(buf, 10, &nt->np.remote_port); if (ret < 0) goto out_unlock; - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -896,7 +896,7 @@ static ssize_t local_ip_store(struct config_item *item, const char *buf, goto out_unlock; nt->np.ipv6 = !!ipv6; - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -921,7 +921,7 @@ static ssize_t remote_ip_store(struct config_item *item, const char *buf, goto out_unlock; nt->np.ipv6 = !!ipv6; - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -957,7 +957,7 @@ static ssize_t remote_mac_store(struct config_item *item, const char *buf, goto out_unlock; memcpy(nt->np.remote_mac, remote_mac, ETH_ALEN); - ret = strnlen(buf, count); + ret = count; out_unlock: dynamic_netconsole_mutex_unlock(); return ret; @@ -1133,7 +1133,7 @@ static ssize_t sysdata_msgid_enabled_store(struct config_item *item, disable_sysdata_feature(nt, SYSDATA_MSGID); unlock_ok: - ret = strnlen(buf, count); + ret = count; dynamic_netconsole_mutex_unlock(); mutex_unlock(&netconsole_subsys.su_mutex); return ret; @@ -1162,7 +1162,7 @@ static ssize_t sysdata_release_enabled_store(struct config_item *item, disable_sysdata_feature(nt, SYSDATA_RELEASE); unlock_ok: - ret = strnlen(buf, count); + ret = count; dynamic_netconsole_mutex_unlock(); mutex_unlock(&netconsole_subsys.su_mutex); return ret; @@ -1191,7 +1191,7 @@ static ssize_t sysdata_taskname_enabled_store(struct config_item *item, disable_sysdata_feature(nt, SYSDATA_TASKNAME); unlock_ok: - ret = strnlen(buf, count); + ret = count; dynamic_netconsole_mutex_unlock(); mutex_unlock(&netconsole_subsys.su_mutex); return ret; @@ -1225,7 +1225,7 @@ static ssize_t sysdata_cpu_nr_enabled_store(struct config_item *item, disable_sysdata_feature(nt, SYSDATA_CPU_NR); unlock_ok: - ret = strnlen(buf, count); + ret = count; dynamic_netconsole_mutex_unlock(); mutex_unlock(&netconsole_subsys.su_mutex); return ret;