Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: x86/kexec: Disable KCOV instrumentation after load_segments() The load_segments() function changes segment registers, invalidating GS base (which KCOV relies on for per-cpu data). When CONFIG_KCOV is enabled, any subsequent instrumented C code call (e.g. native_gdt_invalidate()) begins crashing the kernel in an endless loop. To reproduce the problem, it's sufficient to do kexec on a KCOV-instrumented kernel: $ kexec -l /boot/otherKernel $ kexec -e The real-world context for this problem is enabling crash dump collection in syzkaller. For this, the tool loads a panic kernel before fuzzing and then calls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC and CONFIG_KCOV to be enabled simultaneously. Adding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc()) is also undesirable as it would introduce an extra performance overhead. Disabling instrumentation for the individual functions would be too fragile, so disable KCOV instrumentation for the entire machine_kexec_64.c and physaddr.c. If coverage-guided fuzzing ever needs these components in the future, other approaches should be considered. The problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported there. [ bp: Space out comment for better readability. ]
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef before 0e96cd314c0d819c1635d68125a4d77852c2162e; affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef before 593d67032544b9271094fc9b43e437e017cb2b2f; affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef before 1e3e98596c2769721ade0418434852fb3af4849a; affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef before de05c66fab8847237a9ca216934e56d3ee837f08; affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef before 917e3ad3321e75ca0223d5ccf26ceda116aa51e1 |
| Linux / Linux | affected 6.6; unaffected 0 before 6.6; unaffected 6.6.143 through 6.6.*; unaffected 6.12.93 through 6.12.*; unaffected 6.18.22 through 6.18.*; unaffected 6.19.12 through 6.19.*; unaffected 7.0 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/0e96cd314c0d819c1635d68125a4d77852c2162e
- https://git.kernel.org/stable/c/593d67032544b9271094fc9b43e437e017cb2b2f
- https://git.kernel.org/stable/c/1e3e98596c2769721ade0418434852fb3af4849a
- https://git.kernel.org/stable/c/de05c66fab8847237a9ca216934e56d3ee837f08
- https://git.kernel.org/stable/c/917e3ad3321e75ca0223d5ccf26ceda116aa51e1