diff options
Diffstat (limited to 'arch/x86/kernel/signal.c')
| -rw-r--r-- | arch/x86/kernel/signal.c | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 31b6f5dddfc2..5f441039b572 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -61,6 +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. */ @@ -84,6 +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) @@ -138,9 +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; } |