projects / thirdparty / kernel / stable-queue.git / blame
| Commit | Line | Data |
|---|---|---|
| 36724c58 GKH |
1 | From 0e110732473e14d6520e49d75d2c88ef7d46fe67 Mon Sep 17 00:00:00 2001 |
| 2 | From: "Borislav Petkov (AMD)" <bp@alien8.de> | |
| 3 | Date: Tue, 2 Apr 2024 16:05:49 +0200 | |
| 4 | Subject: x86/retpoline: Do the necessary fixup to the Zen3/4 srso return thunk for !SRSO | |
| 5 | ||
| 6 | From: Borislav Petkov (AMD) <bp@alien8.de> | |
| 7 | ||
| 8 | commit 0e110732473e14d6520e49d75d2c88ef7d46fe67 upstream. | |
| 9 | ||
| 10 | The srso_alias_untrain_ret() dummy thunk in the !CONFIG_MITIGATION_SRSO | |
| 11 | case is there only for the altenative in CALL_UNTRAIN_RET to have | |
| 12 | a symbol to resolve. | |
| 13 | ||
| 14 | However, testing with kernels which don't have CONFIG_MITIGATION_SRSO | |
| 15 | enabled, leads to the warning in patch_return() to fire: | |
| 16 | ||
| 17 | missing return thunk: srso_alias_untrain_ret+0x0/0x10-0x0: eb 0e 66 66 2e | |
| 18 | WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:826 apply_returns (arch/x86/kernel/alternative.c:826 | |
| 19 | ||
| 20 | Put in a plain "ret" there so that gcc doesn't put a return thunk in | |
| 21 | in its place which special and gets checked. | |
| 22 | ||
| 23 | In addition: | |
| 24 | ||
| 25 | ERROR: modpost: "srso_alias_untrain_ret" [arch/x86/kvm/kvm-amd.ko] undefined! | |
| 26 | make[2]: *** [scripts/Makefile.modpost:145: Module.symvers] Chyba 1 | |
| 27 | make[1]: *** [/usr/src/linux-6.8.3/Makefile:1873: modpost] Chyba 2 | |
| 28 | make: *** [Makefile:240: __sub-make] Chyba 2 | |
| 29 | ||
| 30 | since !SRSO builds would use the dummy return thunk as reported by | |
| 31 | petr.pisar@atlas.cz, https://bugzilla.kernel.org/show_bug.cgi?id=218679. | |
| 32 | ||
| 33 | Reported-by: kernel test robot <oliver.sang@intel.com> | |
| 34 | Closes: https://lore.kernel.org/oe-lkp/202404020901.da75a60f-oliver.sang@intel.com | |
| 35 | Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> | |
| 36 | Link: https://lore.kernel.org/all/202404020901.da75a60f-oliver.sang@intel.com/ | |
| 37 | Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> | |
| 38 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
| 39 | --- | |
| 40 | arch/x86/lib/retpoline.S | 5 ++++- | |
| 41 | 1 file changed, 4 insertions(+), 1 deletion(-) | |
| 42 | ||
| 43 | --- a/arch/x86/lib/retpoline.S | |
| 44 | +++ b/arch/x86/lib/retpoline.S | |
| 45 | @@ -222,8 +222,11 @@ SYM_CODE_END(srso_return_thunk) | |
| 46 | #define JMP_SRSO_UNTRAIN_RET "ud2" | |
| 47 | /* Dummy for the alternative in CALL_UNTRAIN_RET. */ | |
| 48 | SYM_CODE_START(srso_alias_untrain_ret) | |
| 49 | - RET | |
| 50 | + ANNOTATE_UNRET_SAFE | |
| 51 | + ret | |
| 52 | + int3 | |
| 53 | SYM_FUNC_END(srso_alias_untrain_ret) | |
| 54 | +__EXPORT_THUNK(srso_alias_untrain_ret) | |
| 55 | #endif /* CONFIG_CPU_SRSO */ | |
| 56 | ||
| 57 | #ifdef CONFIG_CPU_UNRET_ENTRY |