Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

drbd: reject data replies with an out-of-range payload size

recv_dless_read() receives a P_DATA_REPLY from a peer into the bio of an outstanding read request. The peer-supplied payload length reaches it as the signed int data_size, and two peer-controlled inputs can make it negative. With a negotiated data-integrity-alg the digest length is subtracted first, so a reply whose payload is smaller than the digest underflows data_size. With no integrity algorithm (the default) data_size is assigned from the unsigned h95/h100 wire length and drbdd() never bounds it for a payload-carrying command, so a length above INT_MAX casts it negative; this path needs no non-default feature. The bio receive loop then computes expect = min_t(int, data_size, bv_len), which is negative, and drbd_recv_all_warn(mapped, expect) receives with a size_t of SIZE_MAX into the first mapped page.

The sibling receive path read_in_block() is not affected: it uses an unsigned size and rejects it against DRBD_MAX_BIO_SIZE before receiving. Reject a data reply whose size is negative after the optional digest subtraction, covering both triggers.

Impact: a malicious or man-in-the-middle DRBD peer copies attacker-chosen bytes past a bio page in the receiver, corrupting kernel memory. A node that reads from its peer (a diskless node, or read-balancing to the peer) is exposed in the default configuration; data-integrity-alg is not required.