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

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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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121455.732508792@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-06-23 14:02:11 +02:00 committed by Borislav Petkov
parent fa8c84b77a
commit 371071131c
4 changed files with 1 additions and 24 deletions
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1
arch/x86/include/asm/pkeys.h
View File

@ -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)
{

3
arch/x86/kernel/fpu/core.c
View File

@ -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();
}
/*

17
arch/x86/mm/pkeys.c
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@ -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)
{

4
include/linux/pkeys.h
View File

@ -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 */