ksmbd: fix signededness bug in smb_direct_prepare_negotiation()

Overview

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

ksmbd: fix signededness bug in smb_direct_prepare_negotiation()

smb_direct_prepare_negotiation() casts an unsigned __u32 value from sp->max_recv_size and req->preferred_send_size to a signed int before computing min_t(int, ...). A maliciously provided preferred_send_size of 0x80000000 will return as smaller than max_recv_size, and then be used to set the maximum allowed alowed receive size for the next message.

By sending a second message with a large value (>1420 bytes) the attacker can then achieve a heap buffer overflow.

This fix replaces min_t(int, ...) with min_t(u32)

Affected

• Linux >= 0626e6641f6b467447c81dd7678a69c66f7746cf < 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7
• Linux >= 0626e6641f6b467447c81dd7678a69c66f7746cf < a110dbe928561d440e9e117d17331139a0bedace
• Linux >= 0626e6641f6b467447c81dd7678a69c66f7746cf < ceae058eb707ddd0d68f0872f9d9f23b7c30c37b
• Linux >= 0626e6641f6b467447c81dd7678a69c66f7746cf < 55abc475d096da4a5356b6efb0cfdc6156bc1550
• Linux >= 0626e6641f6b467447c81dd7678a69c66f7746cf < 6b4f875aac344cdd52a1f34cc70ed2f874a65757
• Linux 5.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.