90e35b0a98
Such speculations could use user-controlled %gs base, esp. since FreeBSD supports WRGSBASE instructions. Place LFENCEs on entry for each basic block after the test for previous kernel/user mode on the kernel entry, which prevents the speculation. Code accesses %gs-based PCPU before any serialization instructions are executed, like %cr3 reload for KPTI. With pti disabled, on haswell i7-4770S machine, "syscall_timings getppid" shows when no lfence is added to syscall path: test loop time iterations periteration getppid 0 1.040918865 4643611 0.000000224 getppid 1 1.004985962 4481816 0.000000224 getppid 2 1.005196483 4482363 0.000000224 with lfence: getppid 0 1.043701091 4554779 0.000000229 getppid 1 1.016930328 4438094 0.000000229 getppid 2 1.023223117 4466640 0.000000229 and ministat reports 'No difference proven at 95.0% confidence.' Security: CVE-2019-1125 Sponsored by: The FreeBSD Foundation MFC after: 1 week
FreeBSD Source:
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FreeBSD
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cddl Various commands and libraries under the Common Development
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contrib Packages contributed by 3rd parties.
crypto Cryptography stuff (see crypto/README).
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include System include files.
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