diff options
Diffstat (limited to 'arch/x86/kernel/signal.c')
| -rw-r--r-- | arch/x86/kernel/signal.c | 43 |
1 files changed, 37 insertions, 6 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 1504eb8d25aa..2404233336ab 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -27,6 +27,7 @@ #include <linux/context_tracking.h> #include <linux/entry-common.h> #include <linux/syscalls.h> +#include <linux/rseq.h> #include <asm/processor.h> #include <asm/ucontext.h> @@ -40,6 +41,7 @@ #include <asm/syscall.h> #include <asm/sigframe.h> #include <asm/signal.h> +#include <asm/shstk.h> static inline int is_ia32_compat_frame(struct ksignal *ksig) { @@ -59,6 +61,24 @@ static inline int is_x32_frame(struct ksignal *ksig) } /* + * Enable all pkeys temporarily, so as to ensure that both the current + * execution stack as well as the alternate signal stack are writeable. + * The application can use any of the available pkeys to protect the + * alternate signal stack, and we don't know which one it is, so enable + * all. The PKRU register will be reset to init_pkru later in the flow, + * in fpu__clear_user_states(), and it is the application's responsibility + * to enable the appropriate pkey as the first step in the signal handler + * so that the handler does not segfault. + */ +static inline u32 sig_prepare_pkru(void) +{ + u32 orig_pkru = read_pkru(); + + write_pkru(0); + return orig_pkru; +} + +/* * Set up a signal frame. */ @@ -82,6 +102,7 @@ get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size, unsigned long math_size = 0; unsigned long sp = regs->sp; unsigned long buf_fx = 0; + u32 pkru; /* redzone */ if (!ia32_frame) @@ -136,9 +157,17 @@ get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size, return (void __user *)-1L; } + /* Update PKRU to enable access to the alternate signal stack. */ + pkru = sig_prepare_pkru(); /* save i387 and extended state */ - if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size)) + if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size, pkru)) { + /* + * Restore PKRU to the original, user-defined value; disable + * extra pkeys enabled for the alternate signal stack, if any. + */ + write_pkru(pkru); return (void __user *)-1L; + } return (void __user *)sp; } @@ -182,7 +211,7 @@ get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size, static unsigned long __ro_after_init max_frame_size; static unsigned int __ro_after_init fpu_default_state_size; -void __init init_sigframe_size(void) +static int __init init_sigframe_size(void) { fpu_default_state_size = fpu__get_fpstate_size(); @@ -194,7 +223,9 @@ void __init init_sigframe_size(void) max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); pr_info("max sigframe size: %lu\n", max_frame_size); + return 0; } +early_initcall(init_sigframe_size); unsigned long get_sigframe_size(void) { @@ -224,7 +255,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) { bool stepping, failed; - struct fpu *fpu = ¤t->thread.fpu; + struct fpu *fpu = x86_task_fpu(current); if (v8086_mode(regs)) save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL); @@ -360,7 +391,7 @@ static bool strict_sigaltstack_size __ro_after_init = false; static int __init strict_sas_size(char *arg) { - return kstrtobool(arg, &strict_sigaltstack_size); + return kstrtobool(arg, &strict_sigaltstack_size) == 0; } __setup("strict_sas_size", strict_sas_size); @@ -392,14 +423,14 @@ bool sigaltstack_size_valid(size_t ss_size) if (!fpu_state_size_dynamic() && !strict_sigaltstack_size) return true; - fsize += current->group_leader->thread.fpu.perm.__user_state_size; + fsize += x86_task_fpu(current->group_leader)->perm.__user_state_size; if (likely(ss_size > fsize)) return true; if (strict_sigaltstack_size) return ss_size > fsize; - mask = current->group_leader->thread.fpu.perm.__state_perm; + mask = x86_task_fpu(current->group_leader)->perm.__state_perm; if (mask & XFEATURE_MASK_USER_DYNAMIC) return ss_size > fsize; |