CVE-2024-35841: net: tls, fix WARNIING in __sk_msg_free
In the Linux kernel, the following vulnerability has been resolved:
net: tls, fix WARNIING in __sk_msg_free
A splice with MSG_SPLICE_PAGES will cause tls code to use the
tls_sw_sendmsg_splice path in the TLS sendmsg code to move the user
provided pages from the msg into the msg_pl. This will loop over the
msg until msg_pl is full, checked by sk_msg_full(msg_pl). The user
can also set the MORE flag to hint stack to delay sending until receiving
more pages and ideally a full buffer.
If the user adds more pages to the msg than can fit in the msg_pl
scatterlist (MAX_MSG_FRAGS) we should ignore the MORE flag and send
the buffer anyways.
What actually happens though is we abort the msg to msg_pl scatterlist
setup and then because we forget to set 'full record' indicating we
can no longer consume data without a send we fallthrough to the 'continue'
path which will check if msg_data_left(msg) has more bytes to send and
then attempts to fit them in the already full msg_pl. Then next
iteration of sender doing send will encounter a full msg_pl and throw
the warning in the syzbot report.
To fix simply check if we have a full_record in splice code path and
if not send the msg regardless of MORE flag.
Security readout for executives and security teams
Plain-English summary
CVE-2024-35841 is a Linux kernel TLS handling bug triggered in a splice/send path. The public record describes a kernel warning condition, not confirmed data theft or remote compromise. Business urgency is mainly for Linux systems using kernel TLS features, especially where untrusted local workloads can exercise networking APIs.
Executive priority
Treat as a routine-to-priority kernel maintenance item, not an emergency based on current evidence. Patch in normal Linux update cycles, with faster action for multi-tenant systems, internet-facing infrastructure, and environments running untrusted code.
Technical view
The bug is in Linux kernel net/tls handling of MSG_SPLICE_PAGES. When more pages are added than fit in msg_pl scatterlist, the MORE flag path can continue despite a full msg_pl, causing a warning in __sk_msg_free. Stable kernel commits adjust splice handling to send when a full record cannot be built.
Likely exposure
Exposure appears limited to Linux kernels containing the affected TLS splice logic. The source bundle lists Linux kernel versions including 6.5, 6.6.14, 6.7.2, and 6.8 as affected, but distro backports may differ. Systems not using kernel TLS may have lower practical exposure.
Exploitation context
No CISA KEV listing is provided, and the sources do not claim active exploitation. The description implies a user or process able to drive Linux kernel TLS sendmsg/splice behavior could trigger the condition. Public sources provided do not establish remote exploitability or privilege escalation.
Researcher notes
Evidence is narrow: the record documents a resolved kernel warning in net/tls, with no CVSS, CWE, or confirmed exploit status. Assess exploitability against local workload assumptions and specific distro backports. Avoid assuming impact beyond the described warning without additional vendor analysis.
Mitigation direction
Check Linux vendor advisories for kernel packages containing the referenced stable fixes.
Prioritize updates on hosts running untrusted workloads or kernel TLS-dependent services.
If updates are unavailable, monitor vendor guidance for safe configuration workarounds.
Validation and detection
Inventory Linux kernel versions across servers, containers hosts, and appliances.
Compare running kernels against vendor advisories and the referenced stable commits.
Review kernel logs for related TLS or __sk_msg_free warnings.
Confirm patched kernels are booted, not only installed.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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CVE-2024-35841 mapping review
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