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Miller" , Jiri Benc , Hangbin Liu Subject: [PATCH net] tcp: switch snprintf to scnprintf Date: Thu, 14 Nov 2019 18:28:31 +0800 Message-Id: <20191114102831.23753-1-liuhangbin@gmail.com> X-Mailer: git-send-email 2.19.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org snprintf returns the number of chars that would be written, not number of chars that were actually written. As such, 'offs' may get larger than 'tbl.maxlen', causing the 'tbl.maxlen - offs' being < 0, and since the parameter is size_t, it would overflow. Currently, the buffer is still enough, but for future design, use scnprintf would be safer. Suggested-by: Jiri Benc Signed-off-by: Hangbin Liu --- net/ipv4/sysctl_net_ipv4.c | 14 +++++++------- net/ipv4/tcp_cong.c | 12 ++++++------ net/ipv4/tcp_ulp.c | 6 +++--- 3 files changed, 16 insertions(+), 16 deletions(-) diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 59ded25acd04..ed804cf68026 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -334,14 +334,14 @@ static int proc_tcp_fastopen_key(struct ctl_table *table, int write, user_key[i] = le32_to_cpu(key[i]); for (i = 0; i < n_keys; i++) { - off += snprintf(tbl.data + off, tbl.maxlen - off, - "%08x-%08x-%08x-%08x", - user_key[i * 4], - user_key[i * 4 + 1], - user_key[i * 4 + 2], - user_key[i * 4 + 3]); + off += scnprintf(tbl.data + off, tbl.maxlen - off, + "%08x-%08x-%08x-%08x", + user_key[i * 4], + user_key[i * 4 + 1], + user_key[i * 4 + 2], + user_key[i * 4 + 3]); if (i + 1 < n_keys) - off += snprintf(tbl.data + off, tbl.maxlen - off, ","); + off += scnprintf(tbl.data + off, tbl.maxlen - off, ","); } ret = proc_dostring(&tbl, write, buffer, lenp, ppos); diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index c445a81d144e..d84a09bd0201 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -253,9 +253,9 @@ void tcp_get_available_congestion_control(char *buf, size_t maxlen) rcu_read_lock(); list_for_each_entry_rcu(ca, &tcp_cong_list, list) { - offs += snprintf(buf + offs, maxlen - offs, - "%s%s", - offs == 0 ? "" : " ", ca->name); + offs += scnprintf(buf + offs, maxlen - offs, + "%s%s", + offs == 0 ? "" : " ", ca->name); } rcu_read_unlock(); } @@ -282,9 +282,9 @@ void tcp_get_allowed_congestion_control(char *buf, size_t maxlen) list_for_each_entry_rcu(ca, &tcp_cong_list, list) { if (!(ca->flags & TCP_CONG_NON_RESTRICTED)) continue; - offs += snprintf(buf + offs, maxlen - offs, - "%s%s", - offs == 0 ? "" : " ", ca->name); + offs += scnprintf(buf + offs, maxlen - offs, + "%s%s", + offs == 0 ? "" : " ", ca->name); } rcu_read_unlock(); } diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c index 4849edb62d52..c338cae13842 100644 --- a/net/ipv4/tcp_ulp.c +++ b/net/ipv4/tcp_ulp.c @@ -89,9 +89,9 @@ void tcp_get_available_ulp(char *buf, size_t maxlen) *buf = '\0'; rcu_read_lock(); list_for_each_entry_rcu(ulp_ops, &tcp_ulp_list, list) { - offs += snprintf(buf + offs, maxlen - offs, - "%s%s", - offs == 0 ? "" : " ", ulp_ops->name); + offs += scnprintf(buf + offs, maxlen - offs, + "%s%s", + offs == 0 ? "" : " ", ulp_ops->name); } rcu_read_unlock(); } -- 2.19.2