[PATCH 3/4] x86/um/vdso: Panic when vDSO can not be allocated

[Thomas Weißschuh]

The vDSO address is added to the userspace auxiliary vectors even if the
vDSO was not allocated. When accessing the page, userspace processes
will crash.

Enforce that the allocation works.

Signed-off-by: Thomas Weißschuh <linux at weissschuh.net>
---
 arch/x86/um/vdso/vma.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/um/vdso/vma.c b/arch/x86/um/vdso/vma.c
index dc8dfb2abd80..51a2b9f2eca9 100644
--- a/arch/x86/um/vdso/vma.c
+++ b/arch/x86/um/vdso/vma.c
@@ -10,7 +10,6 @@
 #include <asm/elf.h>
 #include <linux/init.h>
 
-static unsigned int __read_mostly vdso_enabled = 1;
 unsigned long um_vdso_addr;
 static struct page *um_vdso;
 
@@ -25,17 +24,11 @@ static int __init init_vdso(void)
 
 	um_vdso = alloc_page(GFP_KERNEL);
 	if (!um_vdso)
-		goto oom;
+		panic("Cannot allocate vdso\n");
 
 	copy_page(page_address(um_vdso), vdso_start);
 
 	return 0;
-
-oom:
-	printk(KERN_ERR "Cannot allocate vdso\n");
-	vdso_enabled = 0;
-
-	return -ENOMEM;
 }
 subsys_initcall(init_vdso);
 
@@ -48,9 +41,6 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		.pages = &um_vdso,
 	};
 
-	if (!vdso_enabled)
-		return 0;
-
 	if (mmap_write_lock_killable(mm))
 		return -EINTR;
 

-- 
2.51.0