The task's initiall PKRU value is set part for fpu__clear()/ copy_init_pkru_to_fpregs(). It is not part of init_fpstate.xsave and instead it is set explictly. If the user removes the PKRU state from XSAVE in the signal handler then __fpu__restore_sig() will restore the missing bits from `init_fpstate' and initialize the PKRU value to 0.
Add the `init_pkru_value' to `init_fpstate' so it is set to the init value in such a case. In theory we could drop copy_init_pkru_to_fpregs() because restoring the PKRU at return-to-userland should be enough. Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- arch/x86/kernel/cpu/common.c | 5 +++++ arch/x86/mm/pkeys.c | 6 ++++++ 2 files changed, 11 insertions(+) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index cb28e98a0659a..352fa19e63110 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -372,6 +372,8 @@ static bool pku_disabled; static __always_inline void setup_pku(struct cpuinfo_x86 *c) { + struct pkru_state *pk; + /* check the boot processor, plus compile options for PKU: */ if (!cpu_feature_enabled(X86_FEATURE_PKU)) return; @@ -382,6 +384,9 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c) return; cr4_set_bits(X86_CR4_PKE); + pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU); + if (pk) + pk->pkru = init_pkru_value; /* * Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE * cpuid bit to be set. We need to ensure that we diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c index 2ecbf4155f98f..1dcfc91c8f0c3 100644 --- a/arch/x86/mm/pkeys.c +++ b/arch/x86/mm/pkeys.c @@ -18,6 +18,7 @@ #include <asm/cpufeature.h> /* boot_cpu_has, ... */ #include <asm/mmu_context.h> /* vma_pkey() */ +#include <asm/fpu/internal.h> /* init_fpstate */ int __execute_only_pkey(struct mm_struct *mm) { @@ -161,6 +162,7 @@ static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf, static ssize_t init_pkru_write_file(struct file *file, const char __user *user_buf, size_t count, loff_t *ppos) { + struct pkru_state *pk; char buf[32]; ssize_t len; u32 new_init_pkru; @@ -183,6 +185,10 @@ static ssize_t init_pkru_write_file(struct file *file, return -EINVAL; WRITE_ONCE(init_pkru_value, new_init_pkru); + pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU); + if (!pk) + return -EINVAL; + pk->pkru = new_init_pkru; return count; } -- 2.20.1
