Overview
About vulnerability
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.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 5.14.0 (+4 more)
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.