smb: client: fix heap overflow in cifs_do_set_acl()

Overview

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

smb: client: fix heap overflow in cifs_do_set_acl()

cifs_set_acl() validates ACL size using posix_acl_xattr_size():

    4 + (count * 8)  // 4-byte header + 8 bytes per ACE

cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS wire format into the same buffer:

    6 + (count * 10)  // 6-byte header + 10 bytes per ACE

An ACL that passes the xattr-based check in cifs_set_acl() can overflow the heap when posix_acl_to_cifs() writes the larger CIFS format.

Validate the CIFS format size against the remaining buffer space and USHRT_MAX before converting--data_count is __u16, so sizes above USHRT_MAX truncate the on-wire packet length, causing the server to apply a partial ACL. Replace MaxDataCount = 1000 with min(CIFSMaxBufSize, USHRT_MAX).

Affected

• Linux >= dc1af4c4b4721abfa07b351063825acc7e69cc66 < 68652afb9b9adf70125971abee9b95341e042249
• Linux >= dc1af4c4b4721abfa07b351063825acc7e69cc66 < 9312a00215602ba028495ef3fa00fb84af0478e0
• Linux >= dc1af4c4b4721abfa07b351063825acc7e69cc66 < d96f3365ce61c5f39602955af43c8174548dee98
• Linux >= dc1af4c4b4721abfa07b351063825acc7e69cc66 < 596b4062e6c75bdd85a7f2b7f2087a872dc420ac
• Linux >= dc1af4c4b4721abfa07b351063825acc7e69cc66 < 1dac61e2c29d1a71784604b48cf3b1234a65ec29
• Linux 6.2

Remediation

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