x86/um/vdso: Panic when vDSO can not be allocated

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@weissschuh.net>
Link: https://patch.msgid.link/20251013-uml-vdso-cleanup-v1-3-a079c7adcc69@weissschuh.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/arch/x86/um/vdso/vma.c b/arch/x86/um/vdso/vma.c
index dc8dfb2abd8094fd5a0952aa88b03b5bddcd12d9..51a2b9f2eca95d8c07feda7667a883cb7a714efc 100644 (file)
--- 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;