Bug 2297550 (CVE-2024-40966)

Summary: CVE-2024-40966 kernel: tty: add the option to have a tty reject a new ldisc
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: kernel 6.1.96, kernel 6.6.36, kernel 6.9.7, kernel 6.10-rc1 Doc Type: If docs needed, set a value
Doc Text:
A vulnerability was found in the Linux kernel's TTY subsystem, where the option to reject a new ldisc was improperly implemented, which can lead to a situation where the con_write() routine is called while holding a spinlock, potentially causing a sleep operation in an invalid context.
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Description OSIDB Bzimport 2024-07-12 13:42:19 UTC 
In the Linux kernel, the following vulnerability has been resolved:

tty: add the option to have a tty reject a new ldisc

... and use it to limit the virtual terminals to just N_TTY.  They are
kind of special, and in particular, the "con_write()" routine violates
the "writes cannot sleep" rule that some ldiscs rely on.

This avoids the

   BUG: sleeping function called from invalid context at kernel/printk/printk.c:2659

when N_GSM has been attached to a virtual console, and gsmld_write()
calls con_write() while holding a spinlock, and con_write() then tries
to get the console lock.
Comment 11 errata-xmlrpc 2024-11-12 09:36:17 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2024:9315 https://access.redhat.com/errata/RHSA-2024:9315