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mm/usercopy: Detect vmalloc overruns

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If you have a vmalloc() allocation, or an address from calling vmap(),
you cannot overrun the vm_area which describes it, regardless of the
size of the underlying allocation.  This probably doesn't do much for
security because vmalloc comes with guard pages these days, but it
prevents usercopy aborts when copying to a vmap() of smaller pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220110231530.665970-3-willy@infradead.org
This commit is contained in:
Matthew Wilcox (Oracle) 2022-01-10 23:15:28 +00:00 • committed by Kees Cook
parent 4e140f59d2
commit 0aef499f31
1 changed files with 16 additions and 0 deletions
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16
mm/usercopy.c
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@ -17,6 +17,7 @@
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/thread_info.h>
#include <linux/vmalloc.h>
#include <linux/atomic.h>
#include <linux/jump_label.h>
#include <asm/sections.h>
@ -238,6 +239,21 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
return;
}
if (is_vmalloc_addr(ptr)) {
struct vm_struct *area = find_vm_area(ptr);
unsigned long offset;
if (!area) {
usercopy_abort("vmalloc", "no area", to_user, 0, n);
return;
}
offset = ptr - area->addr;
if (offset + n > get_vm_area_size(area))
usercopy_abort("vmalloc", NULL, to_user, offset, n);
return;
}
folio = virt_to_folio(ptr);
if (folio_test_slab(folio)) {