Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d97080eb authored by Nadav Amit's avatar Nadav Amit Committed by Ingo Molnar
Browse files

x86/mm: Save debug registers when loading a temporary mm 



Prevent user watchpoints from mistakenly firing while the temporary mm
is being used. As the addresses of the temporary mm might overlap those
of the user-process, this is necessary to prevent wrong signals or worse
things from happening.

Signed-off-by: default avatarNadav Amit <namit@vmware.com>
Signed-off-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <akpm@linux-foundation.org>
Cc: <ard.biesheuvel@linaro.org>
Cc: <deneen.t.dock@intel.com>
Cc: <kernel-hardening@lists.openwall.com>
Cc: <kristen@linux.intel.com>
Cc: <linux_dti@icloud.com>
Cc: <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190426001143.4983-5-namit@vmware.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent cefa929c

arch/x86/include/asm/mmu_context.h

+23 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <asm/tlbflush.h>

#include <asm/paravirt.h>

#include <asm/mpx.h>

#include <asm/debugreg.h>



extern atomic64_t last_mm_ctx_id;
@@ -380,6 +381,21 @@ static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) 
	lockdep_assert_irqs_disabled();

	temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);

	switch_mm_irqs_off(NULL, mm, current);



	/*

	 * If breakpoints are enabled, disable them while the temporary mm is

	 * used. Userspace might set up watchpoints on addresses that are used

	 * in the temporary mm, which would lead to wrong signals being sent or

	 * crashes.

	 *

	 * Note that breakpoints are not disabled selectively, which also causes

	 * kernel breakpoints (e.g., perf's) to be disabled. This might be

	 * undesirable, but still seems reasonable as the code that runs in the

	 * temporary mm should be short.

	 */

	if (hw_breakpoint_active())

		hw_breakpoint_disable();



	return temp_state;

}
@@ -387,6 +403,13 @@ static inline void unuse_temporary_mm(temp_mm_state_t prev_state) 
{

	lockdep_assert_irqs_disabled();

	switch_mm_irqs_off(NULL, prev_state.mm, current);



	/*

	 * Restore the breakpoints if they were disabled before the temporary mm

	 * was loaded.

	 */

	if (hw_breakpoint_active())

		hw_breakpoint_restore();

}



#endif /* _ASM_X86_MMU_CONTEXT_H */