1From a75fb7b198eed50d769c80c36629f38346882cbf Mon Sep 17 00:00:00 2001 2From: Paul Mackerras <paulus@ozlabs.org> 3Date: Thu, 4 Aug 2022 12:23:08 +1000 4Subject: [PATCH] pppdump: Avoid out-of-range access to packet buffer 5 6This fixes a potential vulnerability where data is written to spkt.buf 7and rpkt.buf without a check on the array index. To fix this, we 8check the array index (pkt->cnt) before storing the byte or 9incrementing the count. This also means we no longer have a potential 10signed integer overflow on the increment of pkt->cnt. 11 12Fortunately, pppdump is not used in the normal process of setting up a 13PPP connection, is not installed setuid-root, and is not invoked 14automatically in any scenario that I am aware of. 15 16Signed-off-by: Paul Mackerras <paulus@ozlabs.org> 17 18Upstream-Status: Backport 19Signed-off-by: Ross Burton <ross.burton@arm.com> 20--- 21 pppdump/pppdump.c | 7 ++++++- 22 1 file changed, 6 insertions(+), 1 deletion(-) 23 24diff --git a/pppdump/pppdump.c b/pppdump/pppdump.c 25index 2b815fc9..b85a8627 100644 26--- a/pppdump/pppdump.c 27+++ b/pppdump/pppdump.c 28@@ -297,6 +297,10 @@ dumpppp(f) 29 printf("%s aborted packet:\n ", dir); 30 q = " "; 31 } 32+ if (pkt->cnt >= sizeof(pkt->buf)) { 33+ printf("%s over-long packet truncated:\n ", dir); 34+ q = " "; 35+ } 36 nb = pkt->cnt; 37 p = pkt->buf; 38 pkt->cnt = 0; 39@@ -400,7 +404,8 @@ dumpppp(f) 40 c ^= 0x20; 41 pkt->esc = 0; 42 } 43- pkt->buf[pkt->cnt++] = c; 44+ if (pkt->cnt < sizeof(pkt->buf)) 45+ pkt->buf[pkt->cnt++] = c; 46 break; 47 } 48 } 49