Commit 27b5d61c authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents ea82593b 59f5ede3

MAINTAINERS

+5 −5
Original line number Diff line number Diff line
@@ -7499,7 +7499,7 @@ F: Documentation/hwmon/f71805f.rst 
F:	drivers/hwmon/f71805f.c









FADDR2LINE









M:	Josh Poimboeuf <jpoimboe@redhat.com>









M:	Josh Poimboeuf <jpoimboe@kernel.org>









S:	Maintained









F:	scripts/faddr2line


















@@ -11348,7 +11348,7 @@ F:	drivers/mmc/host/litex_mmc.c







N:	litex

















LIVE PATCHING









M:	Josh Poimboeuf <jpoimboe@redhat.com>









M:	Josh Poimboeuf <jpoimboe@kernel.org>









M:	Jiri Kosina <jikos@kernel.org>









M:	Miroslav Benes <mbenes@suse.cz>









M:	Petr Mladek <pmladek@suse.com>










@@ -14224,7 +14224,7 @@ F:	lib/objagg.c







F:	lib/test_objagg.c

















OBJTOOL









M:	Josh Poimboeuf <jpoimboe@redhat.com>









M:	Josh Poimboeuf <jpoimboe@kernel.org>









M:	Peter Zijlstra <peterz@infradead.org>









S:	Supported









F:	tools/objtool/










@@ -18792,7 +18792,7 @@ F:	include/dt-bindings/reset/starfive-jh7100.h















STATIC BRANCH/CALL









M:	Peter Zijlstra <peterz@infradead.org>









M:	Josh Poimboeuf <jpoimboe@redhat.com>









M:	Josh Poimboeuf <jpoimboe@kernel.org>









M:	Jason Baron <jbaron@akamai.com>









R:	Steven Rostedt <rostedt@goodmis.org>









R:	Ard Biesheuvel <ardb@kernel.org>










@@ -21444,7 +21444,7 @@ F:	arch/x86/kernel/apic/x2apic_uv_x.c







F:	arch/x86/platform/uv/

















X86 STACK UNWINDING









M:	Josh Poimboeuf <jpoimboe@redhat.com>









M:	Josh Poimboeuf <jpoimboe@kernel.org>









M:	Peter Zijlstra <peterz@infradead.org>









S:	Supported









F:	arch/x86/include/asm/unwind*.h

























arch/x86/kernel/fpu/core.c



+26
−41






























Original line number
Diff line number
Diff line







@@ -41,17 +41,7 @@ struct fpu_state_config fpu_user_cfg __ro_after_init;







 */









struct fpstate init_fpstate __ro_after_init;



















/*









 * Track whether the kernel is using the FPU state









 * currently.









 *









 * This flag is used:









 *









 *   - by IRQ context code to potentially use the FPU









 *     if it's unused.









 *









 *   - to debug kernel_fpu_begin()/end() correctness









 */









/* Track in-kernel FPU usage */









static DEFINE_PER_CPU(bool, in_kernel_fpu);



















/*










@@ -59,42 +49,37 @@ static DEFINE_PER_CPU(bool, in_kernel_fpu);







 */









DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);



















static bool kernel_fpu_disabled(void)









/*









 * Can we use the FPU in kernel mode with the









 * whole "kernel_fpu_begin/end()" sequence?









 */









bool irq_fpu_usable(void)









{









	return this_cpu_read(in_kernel_fpu);









}









	if (WARN_ON_ONCE(in_nmi()))









		return false;



















static bool interrupted_kernel_fpu_idle(void)









{









	return !kernel_fpu_disabled();









}









	/* In kernel FPU usage already active? */









	if (this_cpu_read(in_kernel_fpu))









		return false;



















	/*









 * Were we in user mode (or vm86 mode) when we were









 * interrupted?









	 * When not in NMI or hard interrupt context, FPU can be used in:









	 *









 * Doing kernel_fpu_begin/end() is ok if we are running









 * in an interrupt context from user mode - we'll just









 * save the FPU state as required.









	 * - Task context except from within fpregs_lock()'ed critical









	 *   regions.









	 *









	 * - Soft interrupt processing context which cannot happen









	 *   while in a fpregs_lock()'ed critical region.









	 */









static bool interrupted_user_mode(void)









{









	struct pt_regs *regs = get_irq_regs();









	return regs && user_mode(regs);









}









	if (!in_hardirq())









		return true;



















	/*









 * Can we use the FPU in kernel mode with the









 * whole "kernel_fpu_begin/end()" sequence?









 *









 * It's always ok in process context (ie "not interrupt")









 * but it is sometimes ok even from an irq.









	 * In hard interrupt context it's safe when soft interrupts









	 * are enabled, which means the interrupt did not hit in









	 * a fpregs_lock()'ed critical region.









	 */









bool irq_fpu_usable(void)









{









	return !in_interrupt() ||









		interrupted_user_mode() ||









		interrupted_kernel_fpu_idle();









	return !softirq_count();









}









EXPORT_SYMBOL(irq_fpu_usable);