Bug 2363326 (CVE-2025-37756)

Summary: CVE-2025-37756 kernel: net: tls: explicitly disallow disconnect
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-05-01 14:03:54 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: tls: explicitly disallow disconnect

syzbot discovered that it can disconnect a TLS socket and then
run into all sort of unexpected corner cases. I have a vague
recollection of Eric pointing this out to us a long time ago.
Supporting disconnect is really hard, for one thing if offload
is enabled we'd need to wait for all packets to be _acked_.
Disconnect is not commonly used, disallow it.

The immediate problem syzbot run into is the warning in the strp,
but that's just the easiest bug to trigger:

  WARNING: CPU: 0 PID: 5834 at net/tls/tls_strp.c:486 tls_strp_msg_load+0x72e/0xa80 net/tls/tls_strp.c:486
  RIP: 0010:tls_strp_msg_load+0x72e/0xa80 net/tls/tls_strp.c:486
  Call Trace:
   <TASK>
   tls_rx_rec_wait+0x280/0xa60 net/tls/tls_sw.c:1363
   tls_sw_recvmsg+0x85c/0x1c30 net/tls/tls_sw.c:2043
   inet6_recvmsg+0x2c9/0x730 net/ipv6/af_inet6.c:678
   sock_recvmsg_nosec net/socket.c:1023 [inline]
   sock_recvmsg+0x109/0x280 net/socket.c:1045
   __sys_recvfrom+0x202/0x380 net/socket.c:2237
Comment 1 Avinash Hanwate 2025-05-02 05:38:53 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025050139-CVE-2025-37756-a06e@gregkh/T