Commit-ID: a67e7277d01ccfd39b0db5a198c2643cc19dd79c Gitweb: http://git.kernel.org/tip/a67e7277d01ccfd39b0db5a198c2643cc19dd79c Author: Andy Lutomirski <[email protected]> AuthorDate: Wed, 18 Mar 2015 18:33:29 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 23 Mar 2015 11:13:36 +0100
x86/asm/entry: Add user_mode_ignore_vm86() user_mode() is dangerous and user_mode_vm() has a confusing name. Add user_mode_ignore_vm86() (equivalent to current user_mode()). We'll change the small number of legitimate users of user_mode() to user_mode_ignore_vm86(). Inspired by grsec, although this works rather differently. Signed-off-by: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brad Spengler <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/202c56ca63823c338af8e2e54948dbe222da6343.1426728647.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/ptrace.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 83b874d..4a040f0 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -121,6 +121,23 @@ static inline int user_mode_vm(struct pt_regs *regs) #endif } +/* + * This is the fastest way to check whether regs come from user space. + * It is unsafe if regs might come from vm86 mode, though -- in vm86 + * mode, all bits of CS and SS are completely under the user's control. + * The CPU considers vm86 mode to be CPL 3 regardless of CS and SS. + * + * Do NOT use this function unless you have already ruled out the + * possibility that regs came from vm86 mode. + * + * We check for RPL != 0 instead of RPL == 3 because we don't use rings + * 1 or 2 and this is more efficient. + */ +static inline int user_mode_ignore_vm86(struct pt_regs *regs) +{ + return (regs->cs & SEGMENT_RPL_MASK) != 0; +} + static inline int v8086_mode(struct pt_regs *regs) { #ifdef CONFIG_X86_32 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
