* [PATCH net] net/x25: prevent a couple of overflows [not found] <61d3e7e75f704996bf312ef5d271bcea@tencent.com> @ 2020-11-30 10:04 ` Dan Carpenter 2020-12-01 6:50 ` Martin Schiller 0 siblings, 1 reply; 6+ messages in thread From: Dan Carpenter @ 2020-11-30 10:04 UTC (permalink / raw) To: Andrew Hendry, kiyin(尹亮), Martin Schiller Cc: security@kernel.org, linux-distros@vs.openwall.org, huntchen(陈阳), dannywang(王宇), David S. Miller, Jakub Kicinski, linux-x25, netdev From: "kiyin(尹亮)" <kiyin@tencent.com> The .x25_addr[] address comes from the user and is not necessarily NUL terminated. This leads to a couple problems. The first problem is that the strlen() in x25_bind() can read beyond the end of the buffer. The second problem is more subtle and could result in memory corruption. The call tree is: x25_connect() --> x25_write_internal() --> x25_addr_aton() The .x25_addr[] buffers are copied to the "addresses" buffer from x25_write_internal() so it will lead to stack corruption. The x25 protocol only allows 15 character addresses so putting a NUL terminator as the 16th character is safe and obviously preferable to reading out of bounds. Signed-off-by: "kiyin(尹亮)" <kiyin@tencent.com> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> --- net/x25/af_x25.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index 0bbb283f23c9..3180f15942fe 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -686,6 +686,8 @@ static int x25_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) goto out; } + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; + /* check for the null_x25_address */ if (strcmp(addr->sx25_addr.x25_addr, null_x25_address.x25_addr)) { @@ -779,6 +781,7 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr, goto out; rc = -ENETUNREACH; + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; rt = x25_get_route(&addr->sx25_addr); if (!rt) goto out; -- 2.28.0 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH net] net/x25: prevent a couple of overflows 2020-11-30 10:04 ` [PATCH net] net/x25: prevent a couple of overflows Dan Carpenter @ 2020-12-01 6:50 ` Martin Schiller 2020-12-01 15:15 ` [PATCH net v2] " Dan Carpenter 0 siblings, 1 reply; 6+ messages in thread From: Martin Schiller @ 2020-12-01 6:50 UTC (permalink / raw) To: Dan Carpenter Cc: Andrew Hendry, kiyin(尹亮), security, linux-distros, huntchen(陈阳), dannywang(王宇), David S. Miller, Jakub Kicinski, linux-x25, netdev On 2020-11-30 11:04, Dan Carpenter wrote: > From: "kiyin(尹亮)" <kiyin@tencent.com> > > The .x25_addr[] address comes from the user and is not necessarily > NUL terminated. This leads to a couple problems. The first problem is > that the strlen() in x25_bind() can read beyond the end of the buffer. > > The second problem is more subtle and could result in memory > corruption. > The call tree is: > x25_connect() > --> x25_write_internal() > --> x25_addr_aton() > > The .x25_addr[] buffers are copied to the "addresses" buffer from > x25_write_internal() so it will lead to stack corruption. > > The x25 protocol only allows 15 character addresses so putting a NUL > terminator as the 16th character is safe and obviously preferable to > reading out of bounds. > OK, I see the potential danger. I'm just wondering what is the better approach here to counteract it: 1. check if the string is terminated or exceeds the maximum allowed length and report an error if necessary. 2. always terminate the string at byte 15 as you suggested. > Signed-off-by: "kiyin(尹亮)" <kiyin@tencent.com> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > > net/x25/af_x25.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c > index 0bbb283f23c9..3180f15942fe 100644 > --- a/net/x25/af_x25.c > +++ b/net/x25/af_x25.c > @@ -686,6 +686,8 @@ static int x25_bind(struct socket *sock, struct > sockaddr *uaddr, int addr_len) > goto out; > } > > + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; > + > /* check for the null_x25_address */ > if (strcmp(addr->sx25_addr.x25_addr, null_x25_address.x25_addr)) { > > @@ -779,6 +781,7 @@ static int x25_connect(struct socket *sock, struct > sockaddr *uaddr, > goto out; > > rc = -ENETUNREACH; > + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; > rt = x25_get_route(&addr->sx25_addr); > if (!rt) > goto out; ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH net v2] net/x25: prevent a couple of overflows 2020-12-01 6:50 ` Martin Schiller @ 2020-12-01 15:15 ` Dan Carpenter 2020-12-02 7:43 ` [PATCH net v2] net/x25: prevent a couple of overflows(Internet mail) kiyin(尹亮) 2020-12-02 9:27 ` [PATCH net v2] net/x25: prevent a couple of overflows Martin Schiller 0 siblings, 2 replies; 6+ messages in thread From: Dan Carpenter @ 2020-12-01 15:15 UTC (permalink / raw) To: Martin Schiller Cc: David S. Miller, Jakub Kicinski, linux-x25, netdev, Andrew Hendry, kiyin(尹亮), security, linux-distros, huntchen(陈阳), dannywang(王宇), kernel-janitors The .x25_addr[] address comes from the user and is not necessarily NUL terminated. This leads to a couple problems. The first problem is that the strlen() in x25_bind() can read beyond the end of the buffer. The second problem is more subtle and could result in memory corruption. The call tree is: x25_connect() --> x25_write_internal() --> x25_addr_aton() The .x25_addr[] buffers are copied to the "addresses" buffer from x25_write_internal() so it will lead to stack corruption. Verify that the strings are NUL terminated and return -EINVAL if they are not. Reported-by: "kiyin(尹亮)" <kiyin@tencent.com> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> --- The first patch put a NUL terminator on the end of the string and this patch returns an error instead. I don't have a strong preference, which patch to go with. net/x25/af_x25.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index 9232cdb42ad9..d41fffb2507b 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -675,7 +675,8 @@ static int x25_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) int len, i, rc = 0; if (addr_len != sizeof(struct sockaddr_x25) || - addr->sx25_family != AF_X25) { + addr->sx25_family != AF_X25 || + strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN) { rc = -EINVAL; goto out; } @@ -769,7 +770,8 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr, rc = -EINVAL; if (addr_len != sizeof(struct sockaddr_x25) || - addr->sx25_family != AF_X25) + addr->sx25_family != AF_X25 || + strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN) goto out; rc = -ENETUNREACH; -- 2.29.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* RE: [PATCH net v2] net/x25: prevent a couple of overflows(Internet mail) 2020-12-01 15:15 ` [PATCH net v2] " Dan Carpenter @ 2020-12-02 7:43 ` kiyin(尹亮) 2020-12-02 9:27 ` [PATCH net v2] net/x25: prevent a couple of overflows Martin Schiller 1 sibling, 0 replies; 6+ messages in thread From: kiyin(尹亮) @ 2020-12-02 7:43 UTC (permalink / raw) To: Dan Carpenter, Martin Schiller Cc: David S. Miller, Jakub Kicinski, linux-x25@vger.kernel.org, netdev@vger.kernel.org, Andrew Hendry, security@kernel.org, linux-distros@vs.openwall.org, huntchen(陈阳), dannywang(王宇), kernel-janitors@vger.kernel.org Hi Dan, I think the strnlen is better. the kernel doesn't need to adjust user land mistake by putting a NULL terminator. just return an error to let the user land program fix the wrong address. Regards, kiyin > -----Original Message----- > From: Dan Carpenter [mailto:dan.carpenter@oracle.com] > Sent: Tuesday, December 1, 2020 11:15 PM > To: Martin Schiller <ms@dev.tdt.de> > Cc: David S. Miller <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; > linux-x25@vger.kernel.org; netdev@vger.kernel.org; Andrew Hendry > <andrew.hendry@gmail.com>; kiyin(尹亮) <kiyin@tencent.com>; > security@kernel.org; linux-distros@vs.openwall.org; huntchen(陈阳) > <huntchen@tencent.com>; dannywang(王宇) <dannywang@tencent.com>; > kernel-janitors@vger.kernel.org > Subject: [PATCH net v2] net/x25: prevent a couple of overflows(Internet mail) > > The .x25_addr[] address comes from the user and is not necessarily NUL > terminated. This leads to a couple problems. The first problem is that the > strlen() in x25_bind() can read beyond the end of the buffer. > > The second problem is more subtle and could result in memory corruption. > The call tree is: > x25_connect() > --> x25_write_internal() > --> x25_addr_aton() > > The .x25_addr[] buffers are copied to the "addresses" buffer from > x25_write_internal() so it will lead to stack corruption. > > Verify that the strings are NUL terminated and return -EINVAL if they are not. > > Reported-by: "kiyin(尹亮)" <kiyin@tencent.com> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > The first patch put a NUL terminator on the end of the string and this patch > returns an error instead. I don't have a strong preference, which patch to go > with. > > net/x25/af_x25.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index > 9232cdb42ad9..d41fffb2507b 100644 > --- a/net/x25/af_x25.c > +++ b/net/x25/af_x25.c > @@ -675,7 +675,8 @@ static int x25_bind(struct socket *sock, struct > sockaddr *uaddr, int addr_len) > int len, i, rc = 0; > > if (addr_len != sizeof(struct sockaddr_x25) || > - addr->sx25_family != AF_X25) { > + addr->sx25_family != AF_X25 || > + strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == > X25_ADDR_LEN) { > rc = -EINVAL; > goto out; > } > @@ -769,7 +770,8 @@ static int x25_connect(struct socket *sock, struct > sockaddr *uaddr, > > rc = -EINVAL; > if (addr_len != sizeof(struct sockaddr_x25) || > - addr->sx25_family != AF_X25) > + addr->sx25_family != AF_X25 || > + strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == > X25_ADDR_LEN) > goto out; > > rc = -ENETUNREACH; > -- > 2.29.2 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net v2] net/x25: prevent a couple of overflows 2020-12-01 15:15 ` [PATCH net v2] " Dan Carpenter 2020-12-02 7:43 ` [PATCH net v2] net/x25: prevent a couple of overflows(Internet mail) kiyin(尹亮) @ 2020-12-02 9:27 ` Martin Schiller 2020-12-03 1:27 ` Jakub Kicinski 1 sibling, 1 reply; 6+ messages in thread From: Martin Schiller @ 2020-12-02 9:27 UTC (permalink / raw) To: Dan Carpenter Cc: David S. Miller, Jakub Kicinski, linux-x25, netdev, Andrew Hendry, kiyin(尹亮), security, linux-distros, huntchen(陈阳), dannywang(王宇), kernel-janitors On 2020-12-01 16:15, Dan Carpenter wrote: > The .x25_addr[] address comes from the user and is not necessarily > NUL terminated. This leads to a couple problems. The first problem is > that the strlen() in x25_bind() can read beyond the end of the buffer. > > The second problem is more subtle and could result in memory > corruption. > The call tree is: > x25_connect() > --> x25_write_internal() > --> x25_addr_aton() > > The .x25_addr[] buffers are copied to the "addresses" buffer from > x25_write_internal() so it will lead to stack corruption. > > Verify that the strings are NUL terminated and return -EINVAL if they > are not. > > Reported-by: "kiyin(尹亮)" <kiyin@tencent.com> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > The first patch put a NUL terminator on the end of the string and this > patch returns an error instead. I don't have a strong preference, > which > patch to go with. > > net/x25/af_x25.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c > index 9232cdb42ad9..d41fffb2507b 100644 > --- a/net/x25/af_x25.c > +++ b/net/x25/af_x25.c > @@ -675,7 +675,8 @@ static int x25_bind(struct socket *sock, struct > sockaddr *uaddr, int addr_len) > int len, i, rc = 0; > > if (addr_len != sizeof(struct sockaddr_x25) || > - addr->sx25_family != AF_X25) { > + addr->sx25_family != AF_X25 || > + strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN) > { > rc = -EINVAL; > goto out; > } > @@ -769,7 +770,8 @@ static int x25_connect(struct socket *sock, struct > sockaddr *uaddr, > > rc = -EINVAL; > if (addr_len != sizeof(struct sockaddr_x25) || > - addr->sx25_family != AF_X25) > + addr->sx25_family != AF_X25 || > + strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN) > goto out; > > rc = -ENETUNREACH; Acked-by: Martin Schiller <ms@dev.tdt.de> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net v2] net/x25: prevent a couple of overflows 2020-12-02 9:27 ` [PATCH net v2] net/x25: prevent a couple of overflows Martin Schiller @ 2020-12-03 1:27 ` Jakub Kicinski 0 siblings, 0 replies; 6+ messages in thread From: Jakub Kicinski @ 2020-12-03 1:27 UTC (permalink / raw) To: Martin Schiller Cc: Dan Carpenter, David S. Miller, linux-x25, netdev, Andrew Hendry, kiyin( 尹亮) , security, linux-distros, huntchen(陈阳) , dannywang(王宇) , kernel-janitors On Wed, 02 Dec 2020 10:27:18 +0100 Martin Schiller wrote: > On 2020-12-01 16:15, Dan Carpenter wrote: > > The .x25_addr[] address comes from the user and is not necessarily > > NUL terminated. This leads to a couple problems. The first problem is > > that the strlen() in x25_bind() can read beyond the end of the buffer. > > > > The second problem is more subtle and could result in memory > > corruption. > > The call tree is: > > x25_connect() > > --> x25_write_internal() > > --> x25_addr_aton() > > > > The .x25_addr[] buffers are copied to the "addresses" buffer from > > x25_write_internal() so it will lead to stack corruption. > > > > Verify that the strings are NUL terminated and return -EINVAL if they > > are not. > > > > Reported-by: "kiyin(尹亮)" <kiyin@tencent.com> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > > Acked-by: Martin Schiller <ms@dev.tdt.de> Applied, thanks! ^ permalink raw reply [flat|nested] 6+ messages in thread
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2020-11-30 10:04 ` [PATCH net] net/x25: prevent a couple of overflows Dan Carpenter
2020-12-01 6:50 ` Martin Schiller
2020-12-01 15:15 ` [PATCH net v2] " Dan Carpenter
2020-12-02 7:43 ` [PATCH net v2] net/x25: prevent a couple of overflows(Internet mail) kiyin(尹亮)
2020-12-02 9:27 ` [PATCH net v2] net/x25: prevent a couple of overflows Martin Schiller
2020-12-03 1:27 ` Jakub Kicinski
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