Re: [Crash-utility] [PATCH v2] Fix a segfault by "net" command

Hi Dave, I updated my patch to fix a lack of the function's return value.

-- When a network device has a lot of IP addresses, the "net" command can generate a segmentation fault due to a buffer overflow without this patch. I have seen several vmcores like that in customer support. # for i in {1..250} ; do ifconfig eth1:$i 192.168.1.$i ; done # crash ... crash> net NET_DEVICE NAME IP ADDRESS(ES) ffff88007faab000 lo 127.0.0.1 ffff88003e097000 eth0 192.168.122.182 ffff88003e12b000 eth1 192.168.1.1, 192.168.1.2, ..., 192.168.1.250 ffff88003e12e000 eth2 Segmentation fault (core dumped) Changes in v2: * Fix a lack of return value of get_device_address() Signed-off-by: Kazuhito Hagio <k-hagio(a)ab.jp.nec.com&gt; --- net.c | 50 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 14 deletions(-) diff --git a/net.c b/net.c index bb86963..4199091 100644 --- a/net.c +++ b/net.c @@ -70,7 +70,7 @@ static void show_net_devices_v3(ulong); static void print_neighbour_q(ulong, int); static void get_netdev_info(ulong, struct devinfo *); static void get_device_name(ulong, char *); -static void get_device_address(ulong, char *); +static long get_device_address(ulong, char **, long); static void get_sock_info(ulong, char *); static void dump_arp(void); static void arp_state_to_flags(unsigned char); @@ -441,7 +441,8 @@ show_net_devices(ulong task) { ulong next; long flen; - char buf[BUFSIZE]; + char *buf; + long buflen = BUFSIZE; if (symbol_exists("dev_base_head")) { show_net_devices_v2(task); @@ -459,6 +460,7 @@ show_net_devices(ulong task) if (!net->netdevice || !next) return; + buf = GETBUF(buflen); flen = MAX(VADDR_PRLEN, strlen(net->netdevice)); fprintf(fp, "%s NAME IP ADDRESS(ES)\n", @@ -472,12 +474,14 @@ show_net_devices(ulong task) get_device_name(next, buf); fprintf(fp, "%-6s ", buf); - get_device_address(next, buf); + buflen = get_device_address(next, &buf, buflen); fprintf(fp, "%s\n", buf); readmem(next+net->dev_next, KVADDR, &next, sizeof(void *), "(net_)device.next", FAULT_ON_ERROR); } while (next); + + FREEBUF(buf); } static void @@ -485,13 +489,15 @@ show_net_devices_v2(ulong task) { struct list_data list_data, *ld; char *net_device_buf; - char buf[BUFSIZE]; + char *buf; + long buflen = BUFSIZE; int ndevcnt, i; long flen; if (!net->netdevice) /* initialized in net_init() */ return; + buf = GETBUF(buflen); flen = MAX(VADDR_PRLEN, strlen(net->netdevice)); fprintf(fp, "%s NAME IP ADDRESS(ES)\n", @@ -521,12 +527,13 @@ show_net_devices_v2(ulong task) get_device_name(ld->list_ptr[i], buf); fprintf(fp, "%-6s ", buf); - get_device_address(ld->list_ptr[i], buf); + buflen = get_device_address(ld->list_ptr[i], &buf, buflen); fprintf(fp, "%s\n", buf); } FREEBUF(ld->list_ptr); FREEBUF(net_device_buf); + FREEBUF(buf); } static void @@ -535,13 +542,15 @@ show_net_devices_v3(ulong task) ulong nsproxy_p, net_ns_p; struct list_data list_data, *ld; char *net_device_buf; - char buf[BUFSIZE]; + char *buf; + long buflen = BUFSIZE; int ndevcnt, i; long flen; if (!net->netdevice) /* initialized in net_init() */ return; + buf = GETBUF(buflen); flen = MAX(VADDR_PRLEN, strlen(net->netdevice)); fprintf(fp, "%s NAME IP ADDRESS(ES)\n", @@ -581,12 +590,13 @@ show_net_devices_v3(ulong task) get_device_name(ld->list_ptr[i], buf); fprintf(fp, "%-6s ", buf); - get_device_address(ld->list_ptr[i], buf); + buflen = get_device_address(ld->list_ptr[i], &buf, buflen); fprintf(fp, "%s\n", buf); } FREEBUF(ld->list_ptr); FREEBUF(net_device_buf); + FREEBUF(buf); } /* @@ -869,19 +879,24 @@ get_device_name(ulong devaddr, char *buf) * in_ifaddr->ifa_next points to the next in_ifaddr in the list (if any). * */ -static void -get_device_address(ulong devaddr, char *buf) +static long +get_device_address(ulong devaddr, char **bufp, long buflen) { ulong ip_ptr, ifa_list; struct in_addr ifa_address; + char *buf; + char buf2[BUFSIZE]; + long pos = 0; - BZERO(buf, BUFSIZE); + buf = *bufp; + BZERO(buf, buflen); + BZERO(buf2, BUFSIZE); readmem(devaddr + net->dev_ip_ptr, KVADDR, &ip_ptr, sizeof(ulong), "ip_ptr", FAULT_ON_ERROR); if (!ip_ptr) - return; + return buflen; readmem(ip_ptr + OFFSET(in_device_ifa_list), KVADDR, &ifa_list, sizeof(ulong), "ifa_list", FAULT_ON_ERROR); @@ -891,13 +906,20 @@ get_device_address(ulong devaddr, char *buf) &ifa_address, sizeof(struct in_addr), "ifa_address", FAULT_ON_ERROR); - sprintf(&buf[strlen(buf)], "%s%s", - strlen(buf) ? ", " : "", - inet_ntoa(ifa_address)); + sprintf(buf2, "%s%s", pos ? ", " : "", inet_ntoa(ifa_address)); + if (pos + strlen(buf2) >= buflen) { + RESIZEBUF(*bufp, buflen, buflen * 2); + buf = *bufp; + BZERO(buf + buflen, buflen); + buflen *= 2; + } + BCOPY(buf2, &buf[pos], strlen(buf2)); + pos += strlen(buf2); readmem(ifa_list + OFFSET(in_ifaddr_ifa_next), KVADDR, &ifa_list, sizeof(ulong), "ifa_next", FAULT_ON_ERROR); } + return buflen; } /* -- 1.8.3.1 -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility