Bug 2507214 (CVE-2026-64402)

Summary: CVE-2026-64402 kernel: coresight: ultrasoc-smb: Fix OOB write in smb_sync_perf_buffer()
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: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's coresight ultrasoc-smb component. This vulnerability involves an out-of-bounds write in the `smb_sync_perf_buffer()` function. An attacker could potentially exploit this by causing the system to write data beyond the intended memory buffer, which may lead to system instability or a denial of service (DoS). This occurs because a page index is calculated incorrectly before being properly normalized, allowing the system to access memory outside its allocated boundaries.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-07-25 10:11:03 UTC 
In the Linux kernel, the following vulnerability has been resolved:

coresight: ultrasoc-smb: Fix OOB write in smb_sync_perf_buffer()

When the SMB sink is used as a perf AUX sink, smb_update_buffer() calls
smb_sync_perf_buffer() to copy hardware trace data into the perf AUX ring
buffer pages. It derives pg_idx = head >> PAGE_SHIFT from @head, which is
handle->head, and indexes dst_pages[pg_idx]. The pg_idx %= nr_pages
normalization is only applied after the first loop iteration.

This leaves the initial page index underived from the buffer size, which
can result in an out-of-bounds write past dst_pages[] when head exceeds
the AUX buffer size.

Normalize head modulo the AUX buffer size before deriving the page index
and offset, mirroring tmc_etr_sync_perf_buffer().
Comment 1 TEJ RATHI 2026-07-29 10:39:37 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072530-CVE-2026-64402-af30@gregkh/T