[PATCH] ipvs: fix integer overflow in ftp helper port/address parsing

[PATCH] ipvs: fix integer overflow in ftp helper port/address parsing

[Joas Antonio]

ip_vs_ftp_get_addrport() accumulates decimal digits into a __u16
(hport) and into unsigned char (p[]) without checking for overflow.
A crafted FTP PASV/EPSV response with an over-long port or address
octet wraps the value, so the helper configures the data connection
with a truncated port/address.

The netfilter conntrack FTP helper had the same defect, fixed in
commit 2b413fc689ba ("netfilter: nf_conntrack_ftp: avoid u16
overflows"). Apply the equivalent fix here: widen the port accumulator
to u32 and reject values above 65535, and reject address octets above
255.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: CyberSecurityUP <joasantonio108@gmail.com>
---
 net/netfilter/ipvs/ip_vs_ftp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ftp.c b/net/netfilter/ipvs/ip_vs_ftp.c
index b315c608f..9e3e005a8 100644
--- a/net/netfilter/ipvs/ip_vs_ftp.c
+++ b/net/netfilter/ipvs/ip_vs_ftp.c
@@ -102,7 +102,7 @@ static int ip_vs_ftp_get_addrport(char *data, char
*data_limit,
  char *s, c;
  unsigned char p[6];
  char edelim;
- __u16 hport;
+ __u32 hport;
  int i = 0;

  if (data_limit - data < plen) {
@@ -144,7 +144,11 @@ static int ip_vs_ftp_get_addrport(char *data,
char *data_limit,
  return -1;
  c = *data;
  if (isdigit(c)) {
- p[i] = p[i]*10 + c - '0';
+ unsigned int val = p[i] * 10 + c - '0';
+
+ if (val > 255)
+ return -1;
+ p[i] = val;
  } else if (c == ',' && i < 5) {
  i++;
  p[i] = 0;
@@ -222,6 +226,8 @@ static int ip_vs_ftp_get_addrport(char *data, char
*data_limit,
  if (!isdigit(*s))
  break;
  hport = hport * 10 + *s - '0';
+ if (hport > 65535)
+ return -1;
  }
  if (s == data_limit || !hport || *s != edelim)
  return -1;
--
2.39.5 (Apple Git-154)

Re: [PATCH] ipvs: fix integer overflow in ftp helper port/address parsing

[Pablo Neira Ayuso]

You have to indicate what tree this is targetted to, [PATCH] itself
goes to /dev/null. Please use [PATCH ipvs] instead.

On Thu, Aug 13, 2026 at 01:59:30PM -0300, Joas Antonio wrote:
> ip_vs_ftp_get_addrport() accumulates decimal digits into a __u16
> (hport) and into unsigned char (p[]) without checking for overflow.
> A crafted FTP PASV/EPSV response with an over-long port or address
> octet wraps the value, so the helper configures the data connection
> with a truncated port/address.
> 
> The netfilter conntrack FTP helper had the same defect, fixed in
> commit 2b413fc689ba ("netfilter: nf_conntrack_ftp: avoid u16
> overflows"). Apply the equivalent fix here: widen the port accumulator
> to u32 and reject values above 65535, and reject address octets above
> 255.

Patch is garbled, mangled by MUA.

> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: CyberSecurityUP <joasantonio108@gmail.com>

Use a real name in your Signed-off-by.

> ---
>  net/netfilter/ipvs/ip_vs_ftp.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ftp.c b/net/netfilter/ipvs/ip_vs_ftp.c
> index b315c608f..9e3e005a8 100644
> --- a/net/netfilter/ipvs/ip_vs_ftp.c
> +++ b/net/netfilter/ipvs/ip_vs_ftp.c
> @@ -102,7 +102,7 @@ static int ip_vs_ftp_get_addrport(char *data, char
> *data_limit,
>   char *s, c;
>   unsigned char p[6];
>   char edelim;
> - __u16 hport;
> + __u32 hport;
>   int i = 0;
> 
>   if (data_limit - data < plen) {
> @@ -144,7 +144,11 @@ static int ip_vs_ftp_get_addrport(char *data,
> char *data_limit,
>   return -1;
>   c = *data;
>   if (isdigit(c)) {
> - p[i] = p[i]*10 + c - '0';
> + unsigned int val = p[i] * 10 + c - '0';
> +
> + if (val > 255)
> + return -1;
> + p[i] = val;
>   } else if (c == ',' && i < 5) {
>   i++;
>   p[i] = 0;
> @@ -222,6 +226,8 @@ static int ip_vs_ftp_get_addrport(char *data, char
> *data_limit,
>   if (!isdigit(*s))
>   break;
>   hport = hport * 10 + *s - '0';
> + if (hport > 65535)
> + return -1;
>   }
>   if (s == data_limit || !hport || *s != edelim)
>   return -1;
> --
> 2.39.5 (Apple Git-154)