From a75fb7b198eed50d769c80c36629f38346882cbf Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Thu, 4 Aug 2022 12:23:08 +1000 Subject: [PATCH] pppdump: Avoid out-of-range access to packet buffer This fixes a potential vulnerability where data is written to spkt.buf and rpkt.buf without a check on the array index. To fix this, we check the array index (pkt->cnt) before storing the byte or incrementing the count. This also means we no longer have a potential signed integer overflow on the increment of pkt->cnt. Fortunately, pppdump is not used in the normal process of setting up a PPP connection, is not installed setuid-root, and is not invoked automatically in any scenario that I am aware of. Signed-off-by: Paul Mackerras --- pppdump/pppdump.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/pppdump/pppdump.c b/pppdump/pppdump.c index 2b815fc..b85a862 100644 --- a/pppdump/pppdump.c +++ b/pppdump/pppdump.c @@ -297,6 +297,10 @@ dumpppp(f) printf("%s aborted packet:\n ", dir); q = " "; } + if (pkt->cnt >= sizeof(pkt->buf)) { + printf("%s over-long packet truncated:\n ", dir); + q = " "; + } nb = pkt->cnt; p = pkt->buf; pkt->cnt = 0; @@ -400,7 +404,8 @@ dumpppp(f) c ^= 0x20; pkt->esc = 0; } - pkt->buf[pkt->cnt++] = c; + if (pkt->cnt < sizeof(pkt->buf)) + pkt->buf[pkt->cnt++] = c; break; } } -- 2.39.2