| Message ID | 20170524102620.13806-1-mjurczyk@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Samuel Ortiz |
| Headers | show |
On Wed, May 24, 2017 at 3:26 AM, Mateusz Jurczyk <mjurczyk@google.com> wrote: > Fix the sockaddr length verification in the connect() handler of NFC/LLCP > sockets, to compare against the size of the actual structure expected on > input (sockaddr_nfc_llcp) instead of its shorter version (sockaddr_nfc). > > Both structures are defined in include/uapi/linux/nfc.h. The fields > specific to the _llcp extended struct are as follows: > > 276 __u8 dsap; /* Destination SAP, if known */ > 277 __u8 ssap; /* Source SAP to be bound to */ > 278 char service_name[NFC_LLCP_MAX_SERVICE_NAME]; /* Service name URI */; > 279 size_t service_name_len; > > If the caller doesn't provide a sufficiently long sockaddr buffer, these > fields remain uninitialized (and they currently originate from the stack > frame of the top-level sys_connect handler). They are then copied by > llcp_sock_connect() into internal storage (nfc_llcp_sock structure), and > could be subsequently read back through the user-mode getsockname() > function (handled by llcp_sock_getname()). This would result in the > disclosure of up to ~70 uninitialized bytes from the kernel stack to > user-mode clients capable of creating AFC_NFC sockets. > > Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com> Acked-by: Kees Cook <keescook@chromium.org> -Kees > --- > net/nfc/llcp_sock.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c > index 2ffb18e73df6..d0d12bea65cb 100644 > --- a/net/nfc/llcp_sock.c > +++ b/net/nfc/llcp_sock.c > @@ -662,8 +662,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr, > > pr_debug("sock %p sk %p flags 0x%x\n", sock, sk, flags); > > - if (!addr || len < sizeof(struct sockaddr_nfc) || > - addr->sa_family != AF_NFC) > + if (!addr || len < sizeof(*addr) || addr->sa_family != AF_NFC) > return -EINVAL; > > if (addr->service_name_len == 0 && addr->dsap == 0) > -- > 2.13.0.219.gdb65acc882-goog >
Hi Mateusz, On Wed, May 24, 2017 at 12:26:20PM +0200, Mateusz Jurczyk wrote: > Fix the sockaddr length verification in the connect() handler of NFC/LLCP > sockets, to compare against the size of the actual structure expected on > input (sockaddr_nfc_llcp) instead of its shorter version (sockaddr_nfc). > > Both structures are defined in include/uapi/linux/nfc.h. The fields > specific to the _llcp extended struct are as follows: > > 276 __u8 dsap; /* Destination SAP, if known */ > 277 __u8 ssap; /* Source SAP to be bound to */ > 278 char service_name[NFC_LLCP_MAX_SERVICE_NAME]; /* Service name URI */; > 279 size_t service_name_len; > > If the caller doesn't provide a sufficiently long sockaddr buffer, these > fields remain uninitialized (and they currently originate from the stack > frame of the top-level sys_connect handler). They are then copied by > llcp_sock_connect() into internal storage (nfc_llcp_sock structure), and > could be subsequently read back through the user-mode getsockname() > function (handled by llcp_sock_getname()). This would result in the > disclosure of up to ~70 uninitialized bytes from the kernel stack to > user-mode clients capable of creating AFC_NFC sockets. > > Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com> > --- > net/nfc/llcp_sock.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) Applied to nfc-next, thanks. Cheers, Samuel.
diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c index 2ffb18e73df6..d0d12bea65cb 100644 --- a/net/nfc/llcp_sock.c +++ b/net/nfc/llcp_sock.c @@ -662,8 +662,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr, pr_debug("sock %p sk %p flags 0x%x\n", sock, sk, flags); - if (!addr || len < sizeof(struct sockaddr_nfc) || - addr->sa_family != AF_NFC) + if (!addr || len < sizeof(*addr) || addr->sa_family != AF_NFC) return -EINVAL; if (addr->service_name_len == 0 && addr->dsap == 0)
Fix the sockaddr length verification in the connect() handler of NFC/LLCP sockets, to compare against the size of the actual structure expected on input (sockaddr_nfc_llcp) instead of its shorter version (sockaddr_nfc). Both structures are defined in include/uapi/linux/nfc.h. The fields specific to the _llcp extended struct are as follows: 276 __u8 dsap; /* Destination SAP, if known */ 277 __u8 ssap; /* Source SAP to be bound to */ 278 char service_name[NFC_LLCP_MAX_SERVICE_NAME]; /* Service name URI */; 279 size_t service_name_len; If the caller doesn't provide a sufficiently long sockaddr buffer, these fields remain uninitialized (and they currently originate from the stack frame of the top-level sys_connect handler). They are then copied by llcp_sock_connect() into internal storage (nfc_llcp_sock structure), and could be subsequently read back through the user-mode getsockname() function (handled by llcp_sock_getname()). This would result in the disclosure of up to ~70 uninitialized bytes from the kernel stack to user-mode clients capable of creating AFC_NFC sockets. Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com> --- net/nfc/llcp_sock.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)