ksmbd: fix OOB write in QUERY_INFO for compound requests

Overview

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

ksmbd: fix OOB write in QUERY_INFO for compound requests

When a compound request such as READ + QUERY_INFO(Security) is received, and the first command (READ) consumes most of the response buffer, ksmbd could write beyond the allocated buffer while building a security descriptor.

The root cause was that smb2_get_info_sec() checked buffer space using ppntsd_size from xattr, while build_sec_desc() often synthesized a significantly larger descriptor from POSIX ACLs.

This patch introduces smb_acl_sec_desc_scratch_len() to accurately compute the final descriptor size beforehand, performs proper buffer checking with smb2_calc_max_out_buf_len(), and uses exact-sized allocation + iov pinning.

Affected

• Linux >= 9f297df20d93411c0b4ddad7f88ba04a7cd36e77 < 533f84264e28c54a79257ea87d2f94a0fcc9a611
• Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < 850452af77f55d185f9445e1f7a1db53c5e4aad4
• Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09
• Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < 075ea208c648cc2bcd616295b711d3637c61de45
• Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < 515c2daab46021221bdf406bef19bc90a44ec617
• Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < fda9522ed6afaec45cabc198d8492270c394c7bc
• Linux f2283680a80571ca82d710bc6ecd8f8beac67d63
• Linux >= 6.1.71 < 6.1.191
• Linux >= 5.15.145 < 5.16
• Linux 6.6

Remediation

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