diff options
| author | Eric Biggers <ebiggers@google.com> | 2019-09-05 19:36:37 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2019-09-07 17:44:25 +0200 |
| commit | fe163e534e5eecdfd7b5920b0dfd24c458ee85d6 (patch) | |
| tree | a40b9991bbc07e692093366b568090dcedbceea9 | |
| parent | 1c2977c094998de032fee6e898c88b4a05483d08 (diff) | |
isdn/capi: check message length in capi_write()
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>
| -rw-r--r-- | drivers/isdn/capi/capi.c | 10 | ||||
| -rw-r--r-- | include/uapi/linux/isdn/capicmd.h | 1 |
2 files changed, 10 insertions, 1 deletions
diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c index 3c3ad42f22bf..c92b405b7646 100644 --- a/drivers/isdn/capi/capi.c +++ b/drivers/isdn/capi/capi.c @@ -688,6 +688,9 @@ capi_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos if (!cdev->ap.applid) return -ENODEV; + if (count < CAPIMSG_BASELEN) + return -EINVAL; + skb = alloc_skb(count, GFP_USER); if (!skb) return -ENOMEM; @@ -698,7 +701,8 @@ capi_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos } 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; } @@ -711,6 +715,10 @@ capi_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos 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); diff --git a/include/uapi/linux/isdn/capicmd.h b/include/uapi/linux/isdn/capicmd.h index 4941628a4fb9..5ec88e7548a9 100644 --- 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 |