Commit 37107113 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

x86/fpu: Use pkru_write_default() in copy_init_fpstate_to_fpregs() 



There is no point in using copy_init_pkru_to_fpregs() which in turn calls
write_pkru(). write_pkru() tries to fiddle with the task's xstate buffer
for nothing because the XRSTOR[S](init_fpstate) just cleared the xfeature
flag in the xstate header which makes get_xsave_addr() fail.

It's a useless exercise anyway because the reinitialization activates the
FPU so before the task's xstate buffer can be used again a XRSTOR[S] must
happen which in turn dumps the PKRU value.

Get rid of the now unused copy_init_pkru_to_fpregs().

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121455.732508792@linutronix.de
parent fa8c84b7

arch/x86/include/asm/pkeys.h

+0 −1
Original line number Diff line number Diff line
@@ -124,7 +124,6 @@ extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, 
		unsigned long init_val);

extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,

		unsigned long init_val);

extern void copy_init_pkru_to_fpregs(void);



static inline int vma_pkey(struct vm_area_struct *vma)

{

arch/x86/kernel/fpu/core.c

+1 −2
Original line number Diff line number Diff line
@@ -311,8 +311,7 @@ static inline void restore_fpregs_from_init_fpstate(u64 features_mask) 
	else

		frstor(&init_fpstate.fsave);



	if (cpu_feature_enabled(X86_FEATURE_OSPKE))

		copy_init_pkru_to_fpregs();

	pkru_write_default();

}



/*

arch/x86/mm/pkeys.c

+0 −17
Original line number Diff line number Diff line
@@ -10,7 +10,6 @@ 


#include <asm/cpufeature.h>             /* boot_cpu_has, ...            */

#include <asm/mmu_context.h>            /* vma_pkey()                   */

#include <asm/pkru.h>			/* read/write_pkru()		*/



int __execute_only_pkey(struct mm_struct *mm)

{
@@ -125,22 +124,6 @@ u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) | 
		      PKRU_AD_KEY(10) | PKRU_AD_KEY(11) | PKRU_AD_KEY(12) |

		      PKRU_AD_KEY(13) | PKRU_AD_KEY(14) | PKRU_AD_KEY(15);



/*

 * Called from the FPU code when creating a fresh set of FPU

 * registers.  This is called from a very specific context where

 * we know the FPU registers are safe for use and we can use PKRU

 * directly.

 */

void copy_init_pkru_to_fpregs(void)

{

	u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);

	/*

	 * Override the PKRU state that came from 'init_fpstate'

	 * with the baseline from the process.

	 */

	write_pkru(init_pkru_value_snapshot);

}



static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf,

			     size_t count, loff_t *ppos)

{

include/linux/pkeys.h

+0 −4
Original line number Diff line number Diff line
@@ -44,10 +44,6 @@ static inline bool arch_pkeys_enabled(void) 
	return false;

}



static inline void copy_init_pkru_to_fpregs(void)

{

}



#endif /* ! CONFIG_ARCH_HAS_PKEYS */



#endif /* _LINUX_PKEYS_H */