lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 05 Oct 2021 10:57:54 -0000
From:   "tip-bot2 for Vegard Nossum" <>
Cc:     Vegard Nossum <>,
        Borislav Petkov <>,,,
Subject: [tip: x86/urgent] x86/entry: Clear X86_FEATURE_SMAP when CONFIG_X86_SMAP=n

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     de85c350dde63d7f554d91c333d57ce6ad3bfc62
Author:        Vegard Nossum <>
AuthorDate:    Mon, 04 Oct 2021 00:34:23 +02:00
Committer:     Borislav Petkov <>
CommitterDate: Tue, 05 Oct 2021 12:37:45 +02:00

x86/entry: Clear X86_FEATURE_SMAP when CONFIG_X86_SMAP=n


  3c73b81a9164 ("x86/entry, selftests: Further improve user entry sanity checks")

added a warning if AC is set when in the kernel.


  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

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 <>
Signed-off-by: Borislav Petkov <>
 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
+		clear_cpu_cap(c, X86_FEATURE_SMAP);

Powered by blists - more mailing lists