From 95c3043008ca8449feb96aba5481fe31c2ea750b Mon Sep 17 00:00:00 2001 From: andrew hendry Date: Mon, 7 Feb 2011 00:08:15 +0000 Subject: [PATCH] x25: possible skb leak on bad facilities Originally x25_parse_facilities returned -1 for an error 0 meaning 0 length facilities >0 the length of the facilities parsed. 5ef41308f94dc ("x25: Prevent crashing when parsing bad X.25 facilities") introduced more error checking in x25_parse_facilities however used 0 to indicate bad parsing a6331d6f9a429 ("memory corruption in X.25 facilities parsing") followed this further for DTE facilities, again using 0 for bad parsing. The meaning of 0 got confused in the callers. If the facilities are messed up we can't determine where the data starts. So patch makes all parsing errors return -1 and ensures callers close and don't use the skb further. Reported-by: Andy Whitcroft Signed-off-by: Andrew Hendry Signed-off-by: David S. Miller --- net/x25/x25_facilities.c | 28 +++++++++++++++++++--------- net/x25/x25_in.c | 14 +++++++++++--- 2 files changed, 30 insertions(+), 12 deletions(-) diff --git a/net/x25/x25_facilities.c b/net/x25/x25_facilities.c index 55187c8f642..406207515b5 100644 --- a/net/x25/x25_facilities.c +++ b/net/x25/x25_facilities.c @@ -27,9 +27,19 @@ #include #include -/* - * Parse a set of facilities into the facilities structures. Unrecognised - * facilities are written to the debug log file. +/** + * x25_parse_facilities - Parse facilities from skb into the facilities structs + * + * @skb: sk_buff to parse + * @facilities: Regular facilites, updated as facilities are found + * @dte_facs: ITU DTE facilities, updated as DTE facilities are found + * @vc_fac_mask: mask is updated with all facilities found + * + * Return codes: + * -1 - Parsing error, caller should drop call and clean up + * 0 - Parse OK, this skb has no facilities + * >0 - Parse OK, returns the length of the facilities header + * */ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask) @@ -62,7 +72,7 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, switch (*p & X25_FAC_CLASS_MASK) { case X25_FAC_CLASS_A: if (len < 2) - return 0; + return -1; switch (*p) { case X25_FAC_REVERSE: if((p[1] & 0x81) == 0x81) { @@ -107,7 +117,7 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, break; case X25_FAC_CLASS_B: if (len < 3) - return 0; + return -1; switch (*p) { case X25_FAC_PACKET_SIZE: facilities->pacsize_in = p[1]; @@ -130,7 +140,7 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, break; case X25_FAC_CLASS_C: if (len < 4) - return 0; + return -1; printk(KERN_DEBUG "X.25: unknown facility %02X, " "values %02X, %02X, %02X\n", p[0], p[1], p[2], p[3]); @@ -139,18 +149,18 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, break; case X25_FAC_CLASS_D: if (len < p[1] + 2) - return 0; + return -1; switch (*p) { case X25_FAC_CALLING_AE: if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1) - return 0; + return -1; dte_facs->calling_len = p[2]; memcpy(dte_facs->calling_ae, &p[3], p[1] - 1); *vc_fac_mask |= X25_MASK_CALLING_AE; break; case X25_FAC_CALLED_AE: if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1) - return 0; + return -1; dte_facs->called_len = p[2]; memcpy(dte_facs->called_ae, &p[3], p[1] - 1); *vc_fac_mask |= X25_MASK_CALLED_AE; diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c index f729f022be6..15de65f0471 100644 --- a/net/x25/x25_in.c +++ b/net/x25/x25_in.c @@ -91,10 +91,10 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp { struct x25_address source_addr, dest_addr; int len; + struct x25_sock *x25 = x25_sk(sk); switch (frametype) { case X25_CALL_ACCEPTED: { - struct x25_sock *x25 = x25_sk(sk); x25_stop_timer(sk); x25->condition = 0x00; @@ -113,14 +113,16 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp &dest_addr); if (len > 0) skb_pull(skb, len); + else if (len < 0) + goto out_clear; len = x25_parse_facilities(skb, &x25->facilities, &x25->dte_facilities, &x25->vc_facil_mask); if (len > 0) skb_pull(skb, len); - else - return -1; + else if (len < 0) + goto out_clear; /* * Copy any Call User Data. */ @@ -144,6 +146,12 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp } return 0; + +out_clear: + x25_write_internal(sk, X25_CLEAR_REQUEST); + x25->state = X25_STATE_2; + x25_start_t23timer(sk); + return 0; } /* -- 2.20.1