RE: [PATCH 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1
> From: devel On Behalf Of > Greg KH > Sent: Tuesday, October 16, 2018 22:07 > > On Wed, Oct 17, 2018 at 03:14:06AM +, k...@linuxonhyperv.com wrote: > > From: Dexuan Cui > > > > The patch fixes: > > > > hv_kvp_daemon.c: In function 'kvp_set_ip_info': > > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes > > into a destination of size 4096 > > ... > > --- a/tools/hv/hv_kvp_daemon.c > > +++ b/tools/hv/hv_kvp_daemon.c > > @@ -1176,7 +1176,7 @@ static int kvp_set_ip_info(char *if_name, struct > hv_kvp_ipaddr_value *new_val) > > int error = 0; > > char if_file[PATH_MAX]; > > FILE *file; > > - char cmd[PATH_MAX]; > > + char cmd[PATH_MAX * 2]; > > Overkill? Well, I found the -Wformat-truncation warning can be suppressed by checking the return value of snprintf, so I'm going to do a new patch for KY to resend like this: @@ -1178,6 +1178,7 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val) FILE *file; char cmd[PATH_MAX]; char *mac_addr; + int str_len; /* * Set the configuration for the specified interface with @@ -1301,8 +1302,19 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val) * invoke the external script to do its magic. */ - snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s", -"hv_set_ifconfig", if_file); + str_len = snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s", +"hv_set_ifconfig", if_file); + + /* +* This is a little overcautious, but it's necessary to suppress some +* false warnings from gcc 8.0.1. +*/ + if (str_len <= 0 || (unsigned int)str_len >= sizeof(cmd)) { + syslog(LOG_ERR, "Cmd '%s' (len=%d) may be too long", + cmd, str_len); + return HV_E_FAIL; + } Thanks, -- Dexuan
RE: [PATCH 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1
> From: devel On Behalf Of > Greg KH > Sent: Tuesday, October 16, 2018 22:07 > > On Wed, Oct 17, 2018 at 03:14:06AM +, k...@linuxonhyperv.com wrote: > > From: Dexuan Cui > > > > The patch fixes: > > > > hv_kvp_daemon.c: In function 'kvp_set_ip_info': > > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes > > into a destination of size 4096 > > ... > > --- a/tools/hv/hv_kvp_daemon.c > > +++ b/tools/hv/hv_kvp_daemon.c > > @@ -1176,7 +1176,7 @@ static int kvp_set_ip_info(char *if_name, struct > hv_kvp_ipaddr_value *new_val) > > int error = 0; > > char if_file[PATH_MAX]; > > FILE *file; > > - char cmd[PATH_MAX]; > > + char cmd[PATH_MAX * 2]; > > Overkill? Well, I found the -Wformat-truncation warning can be suppressed by checking the return value of snprintf, so I'm going to do a new patch for KY to resend like this: @@ -1178,6 +1178,7 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val) FILE *file; char cmd[PATH_MAX]; char *mac_addr; + int str_len; /* * Set the configuration for the specified interface with @@ -1301,8 +1302,19 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val) * invoke the external script to do its magic. */ - snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s", -"hv_set_ifconfig", if_file); + str_len = snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s", +"hv_set_ifconfig", if_file); + + /* +* This is a little overcautious, but it's necessary to suppress some +* false warnings from gcc 8.0.1. +*/ + if (str_len <= 0 || (unsigned int)str_len >= sizeof(cmd)) { + syslog(LOG_ERR, "Cmd '%s' (len=%d) may be too long", + cmd, str_len); + return HV_E_FAIL; + } Thanks, -- Dexuan
Re: [PATCH 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1
On Wed, Oct 17, 2018 at 03:14:06AM +, k...@linuxonhyperv.com wrote: > From: Dexuan Cui > > The patch fixes: > > hv_kvp_daemon.c: In function 'kvp_set_ip_info': > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes > into a destination of size 4096 > > Signed-off-by: Dexuan Cui > Cc: K. Y. Srinivasan > Cc: Haiyang Zhang > Cc: Stephen Hemminger > Cc: > Signed-off-by: K. Y. Srinivasan > --- > tools/hv/hv_kvp_daemon.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c > index bbb2a8ef367c..b7c2cf7eaba5 100644 > --- a/tools/hv/hv_kvp_daemon.c > +++ b/tools/hv/hv_kvp_daemon.c > @@ -1176,7 +1176,7 @@ static int kvp_set_ip_info(char *if_name, struct > hv_kvp_ipaddr_value *new_val) > int error = 0; > char if_file[PATH_MAX]; > FILE *file; > - char cmd[PATH_MAX]; > + char cmd[PATH_MAX * 2]; Overkill?
Re: [PATCH 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1
On Wed, Oct 17, 2018 at 03:14:06AM +, k...@linuxonhyperv.com wrote: > From: Dexuan Cui > > The patch fixes: > > hv_kvp_daemon.c: In function 'kvp_set_ip_info': > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes > into a destination of size 4096 > > Signed-off-by: Dexuan Cui > Cc: K. Y. Srinivasan > Cc: Haiyang Zhang > Cc: Stephen Hemminger > Cc: > Signed-off-by: K. Y. Srinivasan > --- > tools/hv/hv_kvp_daemon.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c > index bbb2a8ef367c..b7c2cf7eaba5 100644 > --- a/tools/hv/hv_kvp_daemon.c > +++ b/tools/hv/hv_kvp_daemon.c > @@ -1176,7 +1176,7 @@ static int kvp_set_ip_info(char *if_name, struct > hv_kvp_ipaddr_value *new_val) > int error = 0; > char if_file[PATH_MAX]; > FILE *file; > - char cmd[PATH_MAX]; > + char cmd[PATH_MAX * 2]; Overkill?