This is a note to let you know that I've just added the patch titled
selftests/x86/iopl: Adjust to the faked iopl CLI/STI usage
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
selftests-x86-iopl-adjust-to-the-faked-iopl-cli-sti-usage.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a72fdfd21e01c626273ddcf5ab740d4caef4be54 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@xxxxxxx>
Date: Fri, 29 Oct 2021 19:27:32 +0200
Subject: selftests/x86/iopl: Adjust to the faked iopl CLI/STI usage
From: Borislav Petkov <bp@xxxxxxx>
commit a72fdfd21e01c626273ddcf5ab740d4caef4be54 upstream.
Commit in Fixes changed the iopl emulation to not #GP on CLI and STI
because it would break some insane luserspace tools which would toggle
interrupts.
The corresponding selftest would rely on the fact that executing CLI/STI
would trigger a #GP and thus detect it this way but since that #GP is
not happening anymore, the detection is now wrong too.
Extend the test to actually look at the IF flag and whether executing
those insns had any effect on it. The STI detection needs to have the
fact that interrupts were previously disabled, passed in so do that from
the previous CLI test, i.e., STI test needs to follow a previous CLI one
for it to make sense.
Fixes: b968e84b509d ("x86/iopl: Fake iopl(3) CLI/STI usage")
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211030083939.13073-1-bp@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/x86/iopl.c | 78 +++++++++++++++++++++++++++----------
1 file changed, 58 insertions(+), 20 deletions(-)
--- a/tools/testing/selftests/x86/iopl.c
+++ b/tools/testing/selftests/x86/iopl.c
@@ -85,48 +85,88 @@ static void expect_gp_outb(unsigned shor
printf("[OK]\toutb to 0x%02hx failed\n", port);
}
-static bool try_cli(void)
+#define RET_FAULTED 0
+#define RET_FAIL 1
+#define RET_EMUL 2
+
+static int try_cli(void)
{
+ unsigned long flags;
+
sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
if (sigsetjmp(jmpbuf, 1) != 0) {
- return false;
+ return RET_FAULTED;
} else {
- asm volatile ("cli");
- return true;
+ asm volatile("cli; pushf; pop %[flags]"
+ : [flags] "=rm" (flags));
+
+ /* X86_FLAGS_IF */
+ if (!(flags & (1 << 9)))
+ return RET_FAIL;
+ else
+ return RET_EMUL;
}
clearhandler(SIGSEGV);
}
-static bool try_sti(void)
+static int try_sti(bool irqs_off)
{
+ unsigned long flags;
+
sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
if (sigsetjmp(jmpbuf, 1) != 0) {
- return false;
+ return RET_FAULTED;
} else {
- asm volatile ("sti");
- return true;
+ asm volatile("sti; pushf; pop %[flags]"
+ : [flags] "=rm" (flags));
+
+ /* X86_FLAGS_IF */
+ if (irqs_off && (flags & (1 << 9)))
+ return RET_FAIL;
+ else
+ return RET_EMUL;
}
clearhandler(SIGSEGV);
}
-static void expect_gp_sti(void)
+static void expect_gp_sti(bool irqs_off)
{
- if (try_sti()) {
+ int ret = try_sti(irqs_off);
+
+ switch (ret) {
+ case RET_FAULTED:
+ printf("[OK]\tSTI faulted\n");
+ break;
+ case RET_EMUL:
+ printf("[OK]\tSTI NOPped\n");
+ break;
+ default:
printf("[FAIL]\tSTI worked\n");
nerrs++;
- } else {
- printf("[OK]\tSTI faulted\n");
}
}
-static void expect_gp_cli(void)
+/*
+ * Returns whether it managed to disable interrupts.
+ */
+static bool test_cli(void)
{
- if (try_cli()) {
+ int ret = try_cli();
+
+ switch (ret) {
+ case RET_FAULTED:
+ printf("[OK]\tCLI faulted\n");
+ break;
+ case RET_EMUL:
+ printf("[OK]\tCLI NOPped\n");
+ break;
+ default:
printf("[FAIL]\tCLI worked\n");
nerrs++;
- } else {
- printf("[OK]\tCLI faulted\n");
+ return true;
}
+
+ return false;
}
int main(void)
@@ -152,8 +192,7 @@ int main(void)
}
/* Make sure that CLI/STI are blocked even with IOPL level 3 */
- expect_gp_cli();
- expect_gp_sti();
+ expect_gp_sti(test_cli());
expect_ok_outb(0x80);
/* Establish an I/O bitmap to test the restore */
@@ -204,8 +243,7 @@ int main(void)
printf("[RUN]\tparent: write to 0x80 (should fail)\n");
expect_gp_outb(0x80);
- expect_gp_cli();
- expect_gp_sti();
+ expect_gp_sti(test_cli());
/* Test the capability checks. */
printf("\tiopl(3)\n");
Patches currently in stable-queue which might be from bp@xxxxxxx are
queue-5.10/selftests-x86-iopl-adjust-to-the-faked-iopl-cli-sti-usage.patch
