Hi, Andy. The final line of /proc/<pid>/maps on x86_64 for native 64-bit
tasks shows an incorrect ending address and incorrect permissions. There
is only a single page mapped in this vsyscall region, and it is accessible
for both read and execute.
The patch below fixes this. (Since 32-bit-compat tasks have a real vma
with correct perms/range, no change is necessary for that scenario.)
Before the patch, a "cat /proc/self/maps | tail -1" shows this:
ffffffffff600000-ffffffffffe00000 ---p 00000000 [...]
After the patch, this is the output:
ffffffffff600000-ffffffffff601000 r-xp 00000000 [...]
Cheers. -ernie
Signed-off-by: Ernie Petrides <[email protected]>
--- linux-2.6.18/arch/x86_64/mm/init.c.orig
+++ linux-2.6.18/arch/x86_64/mm/init.c
@@ -774,14 +774,15 @@ static __init int x8664_sysctl_init(void
__initcall(x8664_sysctl_init);
#endif
-/* A pseudo VMAs to allow ptrace access for the vsyscall page. This only
+/* A pseudo VMA to allow ptrace access for the vsyscall page. This only
covers the 64bit vsyscall page now. 32bit has a real VMA now and does
not need special handling anymore. */
static struct vm_area_struct gate_vma = {
.vm_start = VSYSCALL_START,
- .vm_end = VSYSCALL_END,
- .vm_page_prot = PAGE_READONLY
+ .vm_end = VSYSCALL_START + PAGE_SIZE,
+ .vm_page_prot = PAGE_READONLY_EXEC,
+ .vm_flags = VM_READ | VM_EXEC
};
struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
On Friday 10 November 2006 02:20, Ernie Petrides wrote:
> Hi, Andy. The final line of /proc/<pid>/maps on x86_64 for native 64-bit
> tasks shows an incorrect ending address and incorrect permissions. There
> is only a single page mapped in this vsyscall region, and it is accessible
> for both read and execute.
The range reported is how much address space is reserved, but you're
right it is less.
But I don't like hardcoding a page here -- this will likely be extended
soon. Can you please create a new define VSYSCALL_REAL_LENGTH or similar
in vsyscall.h and use that?
Thanks,
-Andi
On Friday, 10-Nov-2006 at 6:07 +0100, Andi Kleen wrote:
> On Friday 10 November 2006 02:20, Ernie Petrides wrote:
>
> > Hi, Andi. The final line of /proc/<pid>/maps on x86_64 for native 64-bit
> > tasks shows an incorrect ending address and incorrect permissions. There
> > is only a single page mapped in this vsyscall region, and it is accessible
> > for both read and execute.
>
> The range reported is how much address space is reserved, but you're
> right it is less.
>
> But I don't like hardcoding a page here -- this will likely be extended
> soon. Can you please create a new define VSYSCALL_REAL_LENGTH or similar
> in vsyscall.h and use that?
Good idea -- how about the patch below?
Cheers. -ernie
Signed-off-by: Ernie Petrides <[email protected]>
--- linux-2.6.18/arch/x86_64/kernel/vsyscall.c.orig
+++ linux-2.6.18/arch/x86_64/kernel/vsyscall.c
@@ -205,6 +205,7 @@ static void __init map_vsyscall(void)
extern char __vsyscall_0;
unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
+ /* Note that VSYSCALL_MAPPED_PAGES must agree with the code below. */
__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_page0, PAGE_KERNEL_VSYSCALL);
}
--- linux-2.6.18/arch/x86_64/mm/init.c.orig
+++ linux-2.6.18/arch/x86_64/mm/init.c
@@ -774,14 +774,15 @@ static __init int x8664_sysctl_init(void
__initcall(x8664_sysctl_init);
#endif
-/* A pseudo VMAs to allow ptrace access for the vsyscall page. This only
+/* A pseudo VMA to allow ptrace access for the vsyscall page. This only
covers the 64bit vsyscall page now. 32bit has a real VMA now and does
not need special handling anymore. */
static struct vm_area_struct gate_vma = {
.vm_start = VSYSCALL_START,
- .vm_end = VSYSCALL_END,
- .vm_page_prot = PAGE_READONLY
+ .vm_end = VSYSCALL_START + (VSYSCALL_MAPPED_PAGES << PAGE_SHIFT),
+ .vm_page_prot = PAGE_READONLY_EXEC,
+ .vm_flags = VM_READ | VM_EXEC
};
struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
--- linux-2.6.18/include/asm-x86_64/vsyscall.h.orig
+++ linux-2.6.18/include/asm-x86_64/vsyscall.h
@@ -9,6 +9,7 @@ enum vsyscall_num {
#define VSYSCALL_START (-10UL << 20)
#define VSYSCALL_SIZE 1024
#define VSYSCALL_END (-2UL << 20)
+#define VSYSCALL_MAPPED_PAGES 1
#define VSYSCALL_ADDR(vsyscall_nr) (VSYSCALL_START+VSYSCALL_SIZE*(vsyscall_nr))
#ifdef __KERNEL__
On Tuesday 14 November 2006 03:51, Ernie Petrides wrote:
> On Friday, 10-Nov-2006 at 6:07 +0100, Andi Kleen wrote:
>
> > On Friday 10 November 2006 02:20, Ernie Petrides wrote:
> >
> > > Hi, Andi. The final line of /proc/<pid>/maps on x86_64 for native 64-bit
> > > tasks shows an incorrect ending address and incorrect permissions. There
> > > is only a single page mapped in this vsyscall region, and it is accessible
> > > for both read and execute.
> >
> > The range reported is how much address space is reserved, but you're
> > right it is less.
> >
> > But I don't like hardcoding a page here -- this will likely be extended
> > soon. Can you please create a new define VSYSCALL_REAL_LENGTH or similar
> > in vsyscall.h and use that?
>
> Good idea -- how about the patch below?
Added thanks. Probably for .20, i don't think it's critical enough for .19
unless someone feels strongly about it.
-Andi
P.S.: When you retransmit patches please always include the original description
for the changelog too.