Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'x86-urgent-2022-05-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fix from Thomas Gleixner:
"A fix and an email address update:
- Prevent FPU state corruption.
The condition in irq_fpu_usable() grants FPU usage when the FPU is
not used in the kernel. That's just wrong as it does not take the
fpregs_lock()'ed regions into account. If FPU usage happens within
such a region from interrupt context, then the FPU state gets
corrupted.
That's a long standing bug, which got unearthed by the recent
changes to the random code.
- Josh wants to use his kernel.org email address"
* tag 'x86-urgent-2022-05-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/fpu: Prevent FPU state corruption
MAINTAINERS: Update Josh Poimboeuf's email address
+31
-46
+5
-5
MAINTAINERS
+5
-5
MAINTAINERS
···
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F: drivers/hwmon/f71805f.c
7500
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FADDR2LINE
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-
M: Josh Poimboeuf <jpoimboe@redhat.com>
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+
M: Josh Poimboeuf <jpoimboe@kernel.org>
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7503
S: Maintained
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7504
F: scripts/faddr2line
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7505
···
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N: litex
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LIVE PATCHING
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-
M: Josh Poimboeuf <jpoimboe@redhat.com>
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+
M: Josh Poimboeuf <jpoimboe@kernel.org>
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M: Jiri Kosina <jikos@kernel.org>
11353
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M: Miroslav Benes <mbenes@suse.cz>
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11354
M: Petr Mladek <pmladek@suse.com>
···
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F: lib/test_objagg.c
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OBJTOOL
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-
M: Josh Poimboeuf <jpoimboe@redhat.com>
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+
M: Josh Poimboeuf <jpoimboe@kernel.org>
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M: Peter Zijlstra <peterz@infradead.org>
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S: Supported
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F: tools/objtool/
···
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STATIC BRANCH/CALL
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M: Peter Zijlstra <peterz@infradead.org>
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-
M: Josh Poimboeuf <jpoimboe@redhat.com>
18795
+
M: Josh Poimboeuf <jpoimboe@kernel.org>
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M: Jason Baron <jbaron@akamai.com>
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R: Steven Rostedt <rostedt@goodmis.org>
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18798
R: Ard Biesheuvel <ardb@kernel.org>
···
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F: arch/x86/platform/uv/
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X86 STACK UNWINDING
21447
-
M: Josh Poimboeuf <jpoimboe@redhat.com>
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+
M: Josh Poimboeuf <jpoimboe@kernel.org>
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M: Peter Zijlstra <peterz@infradead.org>
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S: Supported
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F: arch/x86/include/asm/unwind*.h
+26
-41
arch/x86/kernel/fpu/core.c
+26
-41
arch/x86/kernel/fpu/core.c
···
41
41
*/
42
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struct fpstate init_fpstate __ro_after_init;
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-
/*
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* Track whether the kernel is using the FPU state
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* currently.
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*
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* This flag is used:
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-
*
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* - by IRQ context code to potentially use the FPU
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* if it's unused.
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*
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* - to debug kernel_fpu_begin()/end() correctness
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-
*/
44
+
/* Track in-kernel FPU usage */
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static DEFINE_PER_CPU(bool, in_kernel_fpu);
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/*
···
49
59
*/
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DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
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61
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-
static bool kernel_fpu_disabled(void)
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-
{
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return this_cpu_read(in_kernel_fpu);
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-
}
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-
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static bool interrupted_kernel_fpu_idle(void)
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-
{
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return !kernel_fpu_disabled();
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-
}
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-
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-
/*
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* Were we in user mode (or vm86 mode) when we were
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* interrupted?
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*
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* Doing kernel_fpu_begin/end() is ok if we are running
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* in an interrupt context from user mode - we'll just
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* save the FPU state as required.
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*/
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static bool interrupted_user_mode(void)
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-
{
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struct pt_regs *regs = get_irq_regs();
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return regs && user_mode(regs);
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-
}
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-
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/*
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* Can we use the FPU in kernel mode with the
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* whole "kernel_fpu_begin/end()" sequence?
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*
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* It's always ok in process context (ie "not interrupt")
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* but it is sometimes ok even from an irq.
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65
*/
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bool irq_fpu_usable(void)
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67
{
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return !in_interrupt() ||
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interrupted_user_mode() ||
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interrupted_kernel_fpu_idle();
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+
if (WARN_ON_ONCE(in_nmi()))
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+
return false;
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+
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+
/* In kernel FPU usage already active? */
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+
if (this_cpu_read(in_kernel_fpu))
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+
return false;
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+
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+
/*
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+
* When not in NMI or hard interrupt context, FPU can be used in:
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+
*
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* - Task context except from within fpregs_lock()'ed critical
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* regions.
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*
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* - Soft interrupt processing context which cannot happen
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* while in a fpregs_lock()'ed critical region.
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+
*/
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+
if (!in_hardirq())
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return true;
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+
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+
/*
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* In hard interrupt context it's safe when soft interrupts
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* are enabled, which means the interrupt did not hit in
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+
* a fpregs_lock()'ed critical region.
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+
*/
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+
return !softirq_count();
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}
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EXPORT_SYMBOL(irq_fpu_usable);
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