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authorEric Biggers <ebiggers@google.com>2019-09-06 05:36:37 +0300
committerDavid S. Miller <davem@davemloft.net>2019-09-07 18:44:25 +0300
commitfe163e534e5eecdfd7b5920b0dfd24c458ee85d6 (patch)
treea40b9991bbc07e692093366b568090dcedbceea9 /drivers/isdn
parent1c2977c094998de032fee6e898c88b4a05483d08 (diff)
downloadlinux-fe163e534e5eecdfd7b5920b0dfd24c458ee85d6.tar.xz
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>
Diffstat (limited to 'drivers/isdn')
-rw-r--r--drivers/isdn/capi/capi.c10
1 files changed, 9 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);