Bug 1227797 (CVE-2024-40935)

Summary: VUL-0: CVE-2024-40935: kernel: cachefiles: flush all requests after setting CACHEFILES_DEAD
Product: [Novell Products] SUSE Security Incidents Reporter: SMASH SMASH <smash_bz>
Component: IncidentsAssignee: Kernel Bugs <kernel-bugs>
Status: NEW --- QA Contact: Security Team bot <security-team>
Severity: Normal    
Priority: P3 - Medium CC: gianluca.gabrielli
Version: unspecified   
Target Milestone: ---   
Hardware: Other   
OS: Other   
URL: https://smash.suse.de/issue/413862/
Whiteboard:
Found By: Security Response Team Services Priority:
Business Priority: Blocker: ---
Marketing QA Status: --- IT Deployment: ---

Description SMASH SMASH 2024-07-15 12:36:36 UTC 
In the Linux kernel, the following vulnerability has been resolved:

cachefiles: flush all requests after setting CACHEFILES_DEAD

In ondemand mode, when the daemon is processing an open request, if the
kernel flags the cache as CACHEFILES_DEAD, the cachefiles_daemon_write()
will always return -EIO, so the daemon can't pass the copen to the kernel.
Then the kernel process that is waiting for the copen triggers a hung_task.

Since the DEAD state is irreversible, it can only be exited by closing
/dev/cachefiles. Therefore, after calling cachefiles_io_error() to mark
the cache as CACHEFILES_DEAD, if in ondemand mode, flush all requests to
avoid the above hungtask. We may still be able to read some of the cached
data before closing the fd of /dev/cachefiles.

Note that this relies on the patch that adds reference counting to the req,
otherwise it may UAF.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-40935
https://www.cve.org/CVERecord?id=CVE-2024-40935
https://git.kernel.org/stable/c/320ba9cbca78be79c912143bbba1d1b35ca55cf0
https://git.kernel.org/stable/c/3bf0b8030296e9ee60d3d4c15849ad9ac0b47081
https://git.kernel.org/stable/c/85e833cd7243bda7285492b0653c3abb1e2e757b
https://git.kernel.org/stable/c/e73fac95084839c5178d97e81c6a2051251bdc00
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-40935.mbox