The following commit has been merged into the core/entry branch of tip: Commit-ID: c5c878125ad5aca199dfc10b1af4010165aaa596 Gitweb: https://git.kernel.org/tip/c5c878125ad5aca199dfc10b1af4010165aaa596 Author: Gabriel Krisman Bertazi <[email protected]> AuthorDate: Fri, 27 Nov 2020 14:32:32 -05:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Wed, 02 Dec 2020 10:32:16 +01:00
x86: vdso: Expose sigreturn address on vdso to the kernel Syscall user redirection requires the signal trampoline code to not be captured, in order to support returning with a locked selector while avoiding recursion back into the signal handler. For ia-32, which has the trampoline in the vDSO, expose the entry points to the kernel, such that it can avoid dispatching syscalls from that region to userspace. Suggested-by: Andy Lutomirski <[email protected]> Signed-off-by: Gabriel Krisman Bertazi <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Reviewed-by: Kees Cook <[email protected]> Reviewed-by: Andy Lutomirski <[email protected]> Acked-by: Andy Lutomirski <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lore.kernel.org/r/[email protected] --- arch/x86/entry/vdso/vdso2c.c | 2 ++ arch/x86/entry/vdso/vdso32/sigreturn.S | 2 ++ arch/x86/entry/vdso/vma.c | 15 +++++++++++++++ arch/x86/include/asm/elf.h | 2 ++ arch/x86/include/asm/vdso.h | 2 ++ 5 files changed, 23 insertions(+) diff --git a/arch/x86/entry/vdso/vdso2c.c b/arch/x86/entry/vdso/vdso2c.c index 7380908..2d0f3d8 100644 --- a/arch/x86/entry/vdso/vdso2c.c +++ b/arch/x86/entry/vdso/vdso2c.c @@ -101,6 +101,8 @@ struct vdso_sym required_syms[] = { {"__kernel_sigreturn", true}, {"__kernel_rt_sigreturn", true}, {"int80_landing_pad", true}, + {"vdso32_rt_sigreturn_landing_pad", true}, + {"vdso32_sigreturn_landing_pad", true}, }; __attribute__((format(printf, 1, 2))) __attribute__((noreturn)) diff --git a/arch/x86/entry/vdso/vdso32/sigreturn.S b/arch/x86/entry/vdso/vdso32/sigreturn.S index c3233ee..1bd068f 100644 --- a/arch/x86/entry/vdso/vdso32/sigreturn.S +++ b/arch/x86/entry/vdso/vdso32/sigreturn.S @@ -18,6 +18,7 @@ __kernel_sigreturn: movl $__NR_sigreturn, %eax SYSCALL_ENTER_KERNEL .LEND_sigreturn: +SYM_INNER_LABEL(vdso32_sigreturn_landing_pad, SYM_L_GLOBAL) nop .size __kernel_sigreturn,.-.LSTART_sigreturn @@ -29,6 +30,7 @@ __kernel_rt_sigreturn: movl $__NR_rt_sigreturn, %eax SYSCALL_ENTER_KERNEL .LEND_rt_sigreturn: +SYM_INNER_LABEL(vdso32_rt_sigreturn_landing_pad, SYM_L_GLOBAL) nop .size __kernel_rt_sigreturn,.-.LSTART_rt_sigreturn .previous diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 50e5d3a..de60cd3 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -436,6 +436,21 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) } #endif +bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs) +{ +#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) + const struct vdso_image *image = current->mm->context.vdso_image; + unsigned long vdso = (unsigned long) current->mm->context.vdso; + + if (in_ia32_syscall() && image == &vdso_image_32) { + if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad || + regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad) + return true; + } +#endif + return false; +} + #ifdef CONFIG_X86_64 static __init int vdso_setup(char *s) { diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 44a9b99..66bdfe8 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -388,6 +388,8 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm, compat_arch_setup_additional_pages(bprm, interpreter, \ (ex->e_machine == EM_X86_64)) +extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs); + /* Do not change the values. See get_align_mask() */ enum align_flags { ALIGN_VA_32 = BIT(0), diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h index bbcdc7b..589f489 100644 --- a/arch/x86/include/asm/vdso.h +++ b/arch/x86/include/asm/vdso.h @@ -27,6 +27,8 @@ struct vdso_image { long sym___kernel_rt_sigreturn; long sym___kernel_vsyscall; long sym_int80_landing_pad; + long sym_vdso32_sigreturn_landing_pad; + long sym_vdso32_rt_sigreturn_landing_pad; }; #ifdef CONFIG_X86_64
