Bug 2348193 (CVE-2021-47649)

Summary: CVE-2021-47649 kernel: udmabuf: validate ubuf->pagecount
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
A vulnerability was found in the Linux kernel in the `udmabuf_create()` function. An improper user-provided argument validation can lead to a `ZERO_PTR` value being passed to the sg_alloc_append_table_from_pages()` function, which attempts a dereference and leads to a kernel crash.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-02-26 03:20:51 UTC 
In the Linux kernel, the following vulnerability has been resolved:

udmabuf: validate ubuf->pagecount

Syzbot has reported GPF in sg_alloc_append_table_from_pages(). The
problem was in ubuf->pages == ZERO_PTR.

ubuf->pagecount is calculated from arguments passed from user-space. If
user creates udmabuf with list.size == 0 then ubuf->pagecount will be
also equal to zero; it causes kmalloc_array() to return ZERO_PTR.

Fix it by validating ubuf->pagecount before passing it to
kmalloc_array().
Comment 1 Avinash Hanwate 2025-02-26 19:46:24 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025022649-CVE-2021-47649-f358@gregkh/T