CVE-2026-46139smb: client: use kzalloc to zero-initialize security descriptor buffer

Official description

In the Linux kernel, the following vulnerability has been resolved: smb: client: use kzalloc to zero-initialize security descriptor buffer Commit 62e7dd0a39c2d ("smb: common: change the data type of num_aces to le16") split struct smb_acl's __le32 num_aces field into __le16 num_aces and __le16 reserved. The reserved field corresponds to Sbz2 in the MS-DTYP ACL wire format, which must be zero [1]. When building an ACL descriptor in build_sec_desc(), we are using a kmalloc()'ed descriptor buffer and writing the fields explicitly using le16() writes now. This never writes to the 2 byte reserved field, leaving it as uninitialized heap data. When the reserved field happens to contain non-zero slab garbage, Samba rejects the security descriptor with "ndr_pull_security_descriptor failed: Range Error", causing chmod to fail with EINVAL. Change kmalloc() to kzalloc() to ensure the entire buffer is zero-initialized. [1] https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-dtyp/20233ed8-a6c6-4097-aafa-dd545ed24428

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4c3ed344a970aad51388ac3b0145b98318f0e21f
• https://git.kernel.org/stable/c/941a1e6eb35440336913afc88a82103291956d5d
• https://git.kernel.org/stable/c/be1ef9512a3f5a755895c24f31b334342f4aa15b
• https://git.kernel.org/stable/c/9bdb2ca31368b7671949dfb94a5d57ffccd01edd
• https://git.kernel.org/stable/c/5e489c6c47a2ac15edbaca153b9348e42c1eacab