| From foo@baz Mon 16 Sep 2019 01:07:00 PM CEST |
| From: Eric Biggers <ebiggers@google.com> |
| Date: Thu, 5 Sep 2019 19:36:37 -0700 |
| Subject: isdn/capi: check message length in capi_write() |
| |
| From: Eric Biggers <ebiggers@google.com> |
| |
| [ Upstream commit fe163e534e5eecdfd7b5920b0dfd24c458ee85d6 ] |
| |
| syzbot reported: |
| |
| BUG: KMSAN: uninit-value in capi_write+0x791/0xa90 drivers/isdn/capi/capi.c:700 |
| CPU: 0 PID: 10025 Comm: syz-executor379 Not tainted 4.20.0-rc7+ #2 |
| Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 |
| Call Trace: |
| __dump_stack lib/dump_stack.c:77 [inline] |
| dump_stack+0x173/0x1d0 lib/dump_stack.c:113 |
| kmsan_report+0x12e/0x2a0 mm/kmsan/kmsan.c:613 |
| __msan_warning+0x82/0xf0 mm/kmsan/kmsan_instr.c:313 |
| capi_write+0x791/0xa90 drivers/isdn/capi/capi.c:700 |
| do_loop_readv_writev fs/read_write.c:703 [inline] |
| do_iter_write+0x83e/0xd80 fs/read_write.c:961 |
| vfs_writev fs/read_write.c:1004 [inline] |
| do_writev+0x397/0x840 fs/read_write.c:1039 |
| __do_sys_writev fs/read_write.c:1112 [inline] |
| __se_sys_writev+0x9b/0xb0 fs/read_write.c:1109 |
| __x64_sys_writev+0x4a/0x70 fs/read_write.c:1109 |
| do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291 |
| entry_SYSCALL_64_after_hwframe+0x63/0xe7 |
| [...] |
| |
| The problem is that capi_write() is reading past the end of the message. |
| Fix it by checking the message's length in the needed places. |
| |
| Reported-and-tested-by: syzbot+0849c524d9c634f5ae66@syzkaller.appspotmail.com |
| Signed-off-by: Eric Biggers <ebiggers@google.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/isdn/capi/capi.c | 10 +++++++++- |
| include/uapi/linux/isdn/capicmd.h | 1 + |
| 2 files changed, 10 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/isdn/capi/capi.c |
| +++ b/drivers/isdn/capi/capi.c |
| @@ -687,6 +687,9 @@ capi_write(struct file *file, const char |
| if (!cdev->ap.applid) |
| return -ENODEV; |
| |
| + if (count < CAPIMSG_BASELEN) |
| + return -EINVAL; |
| + |
| skb = alloc_skb(count, GFP_USER); |
| if (!skb) |
| return -ENOMEM; |
| @@ -697,7 +700,8 @@ capi_write(struct file *file, const char |
| } |
| mlen = CAPIMSG_LEN(skb->data); |
| if (CAPIMSG_CMD(skb->data) == CAPI_DATA_B3_REQ) { |
| - if ((size_t)(mlen + CAPIMSG_DATALEN(skb->data)) != count) { |
| + if (count < CAPI_DATA_B3_REQ_LEN || |
| + (size_t)(mlen + CAPIMSG_DATALEN(skb->data)) != count) { |
| kfree_skb(skb); |
| return -EINVAL; |
| } |
| @@ -710,6 +714,10 @@ capi_write(struct file *file, const char |
| CAPIMSG_SETAPPID(skb->data, cdev->ap.applid); |
| |
| if (CAPIMSG_CMD(skb->data) == CAPI_DISCONNECT_B3_RESP) { |
| + if (count < CAPI_DISCONNECT_B3_RESP_LEN) { |
| + kfree_skb(skb); |
| + return -EINVAL; |
| + } |
| mutex_lock(&cdev->lock); |
| capincci_free(cdev, CAPIMSG_NCCI(skb->data)); |
| mutex_unlock(&cdev->lock); |
| --- a/include/uapi/linux/isdn/capicmd.h |
| +++ b/include/uapi/linux/isdn/capicmd.h |
| @@ -16,6 +16,7 @@ |
| #define CAPI_MSG_BASELEN 8 |
| #define CAPI_DATA_B3_REQ_LEN (CAPI_MSG_BASELEN+4+4+2+2+2) |
| #define CAPI_DATA_B3_RESP_LEN (CAPI_MSG_BASELEN+4+2) |
| +#define CAPI_DISCONNECT_B3_RESP_LEN (CAPI_MSG_BASELEN+4) |
| |
| /*----- CAPI commands -----*/ |
| #define CAPI_ALERT 0x01 |