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AX.25: Fix out-of-bounds read in ax25_connect()

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Checks on `addr_len` and `fsa->fsa_ax25.sax25_ndigis` are insufficient.
ax25_connect() can go out of bounds when `fsa->fsa_ax25.sax25_ndigis`
equals to 7 or 8. Fix it.

This issue has been reported as a KMSAN uninit-value bug, because in such
a case, ax25_connect() reaches into the uninitialized portion of the
`struct sockaddr_storage` statically allocated in __sys_connect().

It is safe to remove `fsa->fsa_ax25.sax25_ndigis > AX25_MAX_DIGIS` because
`addr_len` is guaranteed to be less than or equal to
`sizeof(struct full_sockaddr_ax25)`.

Reported-by: syzbot+c82752228ed975b0a623@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=55ef9d629f3b3d7d70b69558015b63b48d01af66
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peilin Ye 2020-07-22 11:19:01 -04:00 • committed by David S. Miller
parent 26cb7085c8
commit 2f2a7ffad5
1 changed files with 3 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

4
net/ax25/af_ax25.c
View file

@ -1187,7 +1187,9 @@ static int __must_check ax25_connect(struct socket *sock,
if (addr_len > sizeof(struct sockaddr_ax25) && if (addr_len > sizeof(struct sockaddr_ax25) &&
fsa->fsa_ax25.sax25_ndigis != 0) { fsa->fsa_ax25.sax25_ndigis != 0) {
/* Valid number of digipeaters ? */ /* Valid number of digipeaters ? */
if (fsa->fsa_ax25.sax25_ndigis < 1 || fsa->fsa_ax25.sax25_ndigis > AX25_MAX_DIGIS) { if (fsa->fsa_ax25.sax25_ndigis < 1 ||
addr_len < sizeof(struct sockaddr_ax25) +
sizeof(ax25_address) * fsa->fsa_ax25.sax25_ndigis) {
err = -EINVAL; err = -EINVAL;
goto out_release; goto out_release;
} }