CVE-2025-68259

Description

In the Linux kernel, the following vulnerability has been resolved:KVM: SVM: Dont skip unrelated instruction if INT3/INTO is replacedWhen re-injecting a soft interrupt from an INT3, INT0, or (select) INTninstruction, discard the exception and retry the instruction if the codestream is changed (e.g. by a different vCPU) between when the CPUexecutes the instruction and when KVM decodes the instruction to get thenext RIP.As effectively predicted by commit 6ef88d6e36c2 (KVM: SVM: Re-injectINT3/INTO instead of retrying the instruction), failure to verify thatthe correct INTn instruction was decoded can effectively clobber gueststate due to decoding the wrong instruction and thus specifying thewrong next RIP.The bug most often manifests as Oops: int3 panics on static branchchecks in Linux guests. Enabling or disabling a static branch in Linuxuses the kernels text poke code patching mechanism. To modify codewhile other CPUs may be executing that code, Linux (temporarily)replaces the first byte of the original instruction with an int3 (opcode0xcc), then patches in the new code stream except for the first byte,and finally replaces the int3 with the first byte of the new codestream. If a CPU hits the int3, i.e. executes the code while its beingmodified, then the guest kernel must look up the RIP to determine how tohandle the #BP, e.g. by emulating the new instruction. If the RIP isincorrect, then this lookup fails and the guest kernel panics.The bug reproduces almost instantly by hacking the guest kernel torepeatedly check a static branch[1] while running a drgn script[2] onthe host to constantly swap out the memory containing the guests TSS.[1]: https://gist.github.com/osandov/44d17c51c28c0ac998ea0334edf90b5a[2]: https://gist.github.com/osandov/10e45e45afa29b11e0c7209247afc00b

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234