Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB reads parsing symlink error response When a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message() returns success without any length validation, leaving the symlink parsers as the only defense against an untrusted server. symlink_data() walks SMB 3.1.1 error contexts with the loop test "p < end", but reads p->ErrorId at offset 4 and p->ErrorDataLength at offset 0. When the server-controlled ErrorDataLength advances p to within 1-7 bytes of end, the next iteration will read past it. When the matching context is found, sym->SymLinkErrorTag is read at offset 4 from p->ErrorContextData with no check that the symlink header itself fits. smb2_parse_symlink_response() then bounds-checks the substitute name using SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from iov_base. That value is computed as sizeof(smb2_err_rsp) + sizeof(smb2_symlink_err_rsp), which is correct only when ErrorContextCount == 0. With at least one error context the symlink data sits 8 bytes deeper, and each skipped non-matching context shifts it further by 8 + ALIGN(ErrorDataLength, 8). The check is too short, allowing the substitute name read to run past iov_len. The out-of-bound heap bytes are UTF-16-decoded into the symlink target and returned to userspace via readlink(2). Fix this all up by making the loops test require the full context header to fit, rejecting sym if its header runs past end, and bound the substitute name against the actual position of sym->PathBuffer rather than a fixed offset. Because sub_offs and sub_len are 16bits, the pointer math will not overflow here with the new greater-than.

Weaknesses 1

Affected Products 3

References 7

• git.kernel.org https://git.kernel.org/stable/c/043834e72337ee7b4e9685859888623ba1504ac7
• git.kernel.org https://git.kernel.org/stable/c/20ac98f0eb6047edb73c9a27af782bdde08b3757
• git.kernel.org https://git.kernel.org/stable/c/3df690bba28edec865cf7190be10708ad0ddd67e
  Patch
• git.kernel.org https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a
  Patch
• git.kernel.org https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd
  Patch
• git.kernel.org https://git.kernel.org/stable/c/d65a64755a3df68a2fd19d2a81395e9f723aca23
• git.kernel.org https://git.kernel.org/stable/c/e0dd90d14cbbf318157ea8e3fb62ee68a28655ed
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/3df690bba28edec865cf7190be10708ad0ddd67e
  Patch
• git.kernel.org https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a
  Patch
• git.kernel.org https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd
  Patch
• git.kernel.org https://git.kernel.org/stable/c/e0dd90d14cbbf318157ea8e3fb62ee68a28655ed
  Patch