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    Subject[PATCH 4.19 033/313] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit 4fcba7802c3e15a6e56e255871d6c72f829b9dd8 ]

    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

    The "(unsigned int)str_len" is to avoid:

    hv_kvp_daemon.c:1309:30: warning: comparison of integer expressions of
    different signedness: 'int' and 'long unsigned int' [-Wsign-compare]

    Signed-off-by: Dexuan Cui <decui@microsoft.com>
    Cc: K. Y. Srinivasan <kys@microsoft.com>
    Cc: Haiyang Zhang <haiyangz@microsoft.com>
    Cc: Stephen Hemminger <sthemmin@microsoft.com>
    Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/hv/hv_kvp_daemon.c | 15 +++++++++++++--
    1 file changed, 13 insertions(+), 2 deletions(-)

    diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
    index bbb2a8ef367c..d7e06fe0270e 100644
    --- a/tools/hv/hv_kvp_daemon.c
    +++ b/tools/hv/hv_kvp_daemon.c
    @@ -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 +1302,18 @@ 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;
    + }
    +
    if (system(cmd)) {
    syslog(LOG_ERR, "Failed to execute cmd '%s'; error: %d %s",
    cmd, errno, strerror(errno));
    --
    2.19.1


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