The following commit has been merged into the x86/urgent branch of tip: Commit-ID: 3958b9c34c2729597e182cc606cc43942fd19f7c Gitweb: https://git.kernel.org/tip/3958b9c34c2729597e182cc606cc43942fd19f7c Author: Vegard Nossum <vegard.nossum@xxxxxxxxxx> AuthorDate: Mon, 04 Oct 2021 00:34:23 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Wed, 06 Oct 2021 18:46:06 +02:00 x86/entry: Clear X86_FEATURE_SMAP when CONFIG_X86_SMAP=n Commit 3c73b81a9164 ("x86/entry, selftests: Further improve user entry sanity checks") added a warning if AC is set when in the kernel. Commit 662a0221893a3d ("x86/entry: Fix AC assertion") changed the warning to only fire if the CPU supports SMAP. However, the warning can still trigger on a machine that supports SMAP but where it's disabled in the kernel config and when running the syscall_nt selftest, for example: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 49 at irqentry_enter_from_user_mode CPU: 0 PID: 49 Comm: init Tainted: G T 5.15.0-rc4+ #98 e6202628ee053b4f310759978284bd8bb0ce6905 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 RIP: 0010:irqentry_enter_from_user_mode ... Call Trace: ? irqentry_enter ? exc_general_protection ? asm_exc_general_protection ? asm_exc_general_protectio IS_ENABLED(CONFIG_X86_SMAP) could be added to the warning condition, but even this would not be enough in case SMAP is disabled at boot time with the "nosmap" parameter. To be consistent with "nosmap" behaviour, clear X86_FEATURE_SMAP when !CONFIG_X86_SMAP. Found using entry-fuzz + satrandconfig. [ bp: Massage commit message. ] Fixes: 3c73b81a9164 ("x86/entry, selftests: Further improve user entry sanity checks") Fixes: 662a0221893a ("x86/entry: Fix AC assertion") Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20211003223423.8666-1-vegard.nossum@xxxxxxxxxx --- arch/x86/kernel/cpu/common.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 0f88859..b3410f1 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -326,6 +326,7 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c) #ifdef CONFIG_X86_SMAP cr4_set_bits(X86_CR4_SMAP); #else + clear_cpu_cap(c, X86_FEATURE_SMAP); cr4_clear_bits(X86_CR4_SMAP); #endif }
