Linus noticed that the error handling in __arch_setup_additional_pages()
fails to clear the mm VDSO pointer if _install_special_mapping()
fails. In practice there should be no actual bug, because if there's an
error the VDSO pointer is cleared later in arch_setup_additional_pages().
However it's no longer necessary to set the pointer before installing
the mapping. Commit c1bab64360e6 ("powerpc/vdso: Move to
_install_special_mapping() and remove arch_vma_name()") reworked the
code so that the VMA name comes from the vm_special_mapping.name, rather
than relying on arch_vma_name().
So rework the code to only set the VDSO pointer once the mappings have
been installed correctly, and remove the stale comment.
Depends-on: c1bab64360e6 ("powerpc/vdso: Move to _install_special_mapping() and remove arch_vma_name()")
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
---
arch/powerpc/kernel/vdso.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 220a76cae7c1..ee4b9d676cff 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -214,13 +214,6 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int
/* Add required alignment. */
vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
- /*
- * Put vDSO base into mm struct. We need to do this before calling
- * install_special_mapping or the perf counter mmap tracking code
- * will fail to recognise it as a vDSO.
- */
- mm->context.vdso = (void __user *)vdso_base + vvar_size;
-
vma = _install_special_mapping(mm, vdso_base, vvar_size,
VM_READ | VM_MAYREAD | VM_IO |
VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
@@ -240,10 +233,15 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int
vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
VM_READ | VM_EXEC | VM_MAYREAD |
VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
- if (IS_ERR(vma))
+ if (IS_ERR(vma)) {
do_munmap(mm, vdso_base, vvar_size, NULL);
+ return PTR_ERR(vma);
+ }
- return PTR_ERR_OR_ZERO(vma);
+ // Now that the mappings are in place, set the mm VDSO pointer
+ mm->context.vdso = (void __user *)vdso_base + vvar_size;
+
+ return 0;
}
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
@@ -257,8 +255,6 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
return -EINTR;
rc = __arch_setup_additional_pages(bprm, uses_interp);
- if (rc)
- mm->context.vdso = NULL;
mmap_write_unlock(mm);
return rc;
--
2.45.2
