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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 <luto@kernel.org>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201127193238.821364-2-krisman@collabora.com
This commit is contained in:
Gabriel Krisman Bertazi 2020-11-27 14:32:32 -05:00 committed by Thomas Gleixner
parent 01fe185d95
commit c5c878125a
5 changed files with 23 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/entry/vdso/vdso2c.c
View File

@ -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))

2
arch/x86/entry/vdso/vdso32/sigreturn.S
View File

@ -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

15
arch/x86/entry/vdso/vma.c
View File

@ -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)
{

2
arch/x86/include/asm/elf.h
View File

@ -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),

2
arch/x86/include/asm/vdso.h
View File

@ -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