Commit edb4a8bf authored by Michael Ellerman's avatar Michael Ellerman Committed by Andrew Morton
Browse files

powerpc/vdso: refactor error handling 

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 c1bab643 ("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.

Link: https://lkml.kernel.org/r/20240812082605.743814-4-mpe@ellerman.id.au


Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 40b88644

arch/powerpc/kernel/vdso.c

+7 −11
Original line number Diff line number Diff line
@@ -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);

	}



	// Now that the mappings are in place, set the mm VDSO pointer

	mm->context.vdso = (void __user *)vdso_base + vvar_size;



	return PTR_ERR_OR_ZERO(vma);

	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;